61.51 seems pretty clear to me in favor of logging. It's fine that you oppose it in principle, but I disagree that it's a matter of interpretation.
For the sake of the discussion...it is all a matter of interpretation.
I come from a background that mixed the legal profession with aviation, so I learned early on in my flying career that most things in the FARs are not to be taken at just face value and almost everything is open to interpretation. To me, 61.51(e)(1) is one of those that is open to interpretation...
Here is my thought process on determining that you can't need to log PIC time in a tailwheel aircraft before you have the endorsement.
CFR 14 Part 61
Section 61.51(e)(1)
(e) Logging pilot-in-command flight time. (1) A sport, recreational, private, or commercial pilot may log pilot-in-command time only for that flight time during which that person—
(i) Is the sole manipulator of the controls of an aircraft for which the pilot is rated or has privileges;
(ii) Is the sole occupant of the aircraft; or
(iii) Except for a recreational pilot, is acting as pilot in command of an aircraft on which more than one pilot is required under the type certification of the aircraft or the regulations under which the flight is conducted
Notice the bold text. The word is 'may'...not 'must' as you see in 61.51(b) regarding what must be entered in the logged. To me, that is the flag that logging PIC is
not clear cut. The way I was taught, 'may' means that there will be situations where you might not be able to log PIC under the provisions of 61.51(e)(1). Since we are flying a tailwheel aircraft, and there are specific regulations governing a tailwheel endorsement, let's dig a little deeper...
CFR 14 Part 61
Section 61.31(i)
(i) Additional training required for operating tailwheel airplanes.
(1) Except as provided in paragraph (i)(2) of this section, no person may act as pilot in command of a tailwheel airplane unless that person has received and logged flight training from an authorized instructor in a tailwheel airplane and received an endorsement in the person's logbook from an authorized instructor who found the person proficient in the operation of a tailwheel airplane. The flight training must include at least the following maneuvers and procedures:
(i) Normal and crosswind takeoffs and landings;
(ii) Wheel landings (unless the manufacturer has recommended against such landings); and
(iii) Go-around procedures.
(2) The training and endorsement required by paragraph (i)(1) of this section is not required if the person logged pilot-in-command time in a tailwheel airplane before April 15, 1991.
Hmmm...here is something interesting...
Both of these sections refer specifically to
pilot in command. That might be important...
I suggest a further investigation as to what exactly "pilot in command" means...
CFR 14 Part 1
Section 1.1
Pilot in command means the person who:
(1) Has final authority and responsibility for the operation and safety of the flight;
(2) Has been designated as pilot in command before or during the flight; and
(3) Holds the appropriate category, class, and type rating, if appropriate, for the conduct of the flight.
Now we are getting somewhere...
Notice in this definition lists three specific items for the definition of pilot in command. Notice at the end of line (2) the word 'and'. Notice it is not 'or', meaning that all three of these items need to be in place for an individual to be considered "pilot in command".
So, back to 61.31(i)...
Adding in the definition of pilot in command to this regulation makes things a lot clearer.
Although the appropriate category and class rating portion is satisfied...
No person may...
Have final authority and responsibility for the operation and safety of the flight; have been designated as pilot in command before or duirng the flight
...of a tailwheel airplane unless that person has received and logged flight training from an authorized instructor in a tailwheel airplane and received an endorsement in the person's logbook from an authorized instructor who found the person proficient in the operation of a tailwheel airplane.
Seems to me that the only person that can log pilot in command time is the instructor doing the endorsement.
Now that we have established that you are not the pilot in command (as you do not fully satisfy the definition of pilot in command per 1.1) we can revisit 61.51(e)(1) where it states...
A sport, recreational, private, or commercial pilot may log pilot-in-command time...
We will stop right there. Now that we have established that one can not be pilot in command of a tailwheel aircraft unless they have the endorsement, 61.51(e)(1) can be kicked to the curb and 61.51(h) is brought forth as this is the "
flight training from an authorized instructor" as required for the tailwheel endorsement spelled out in 61.31(i).
61.51(e)(1) does seem pretty clear as long as it stands alone. However, when you put it back into the entire context of CFR 14 and use all available information and definitions, it becomes clearer that in this situation, it would be very wise
not to log your training time toward your tailwheel endorsement as PIC. The less of a toehold you give the FAA, the better off you are. Just remember, when the FAA comes after you, they don't throw individual regulations at you, they throw the book at you
