OK, I"m gonna say this one more time... When you don't know the answer to a question, DON'T go writing to the FAA for the answer. You will not get an answer you will like. Worse, as is the case here, you will likely create a written statement that you won't like. AND, that written statement will now explicitly limit everyone else.
By and large, the FAA flight regs were written by pilots, not lawyers and technocrats. They were written for pilots with the goal of upholding certain principles pertaining to safety. Mostly these principles and their concomitant regulations made lots of sense. Sometimes the regs were vague because as any pilot with more than a few hundred hours knows, we live in a world of "it depends". When those same pilot FAA officials were still around to interpret and enforce the laws they themselves had written, all was pretty hunky-dory; The people who wrote the laws understood the spirit of the law they were trying to enforce. They understood WHY they had written the regs in the first place. They knew if something didn't smell right. Decades passed and the FAA's sensible pilots have left the building. Now we have a regulatory body comprised of greater and greater numbers of non-flying, sinecured technocrats who have assumed the enforcement function. They DON'T understand the WHY. Being non-flying, REMF desk jockeys, their primary MO is to buck their way up the chain by writing letters of clarification. They live to get letters of inquiry from folks daft enough to write them. It's perfect: all the officiousness, lots of looking busy, and none of the hassle of ever having to go to an actual flight line and observe actual pilots actually flying. Asserting power, informed or otherwise, becomes is their bread and butter. A technocrat's goal is to get promoted, not to serve aviation's interests. Much like in many university and corporate realms, the volume of paper "published" (read: "moved") is what promotion is based upon... content and consequence be damned.
The great thing about aviation is that, largely, it's rules are enforced after something bad has happened. That gives us all a lot more leeway and freedom than most other parts of society enjoy. It also places the responsibility not to be stupid squarely where it should be... on us, as pilots.
If you enjoy this freedom, stop giving the FAA easy pre-emptive targets by inquiring about specifics. If it's not Kosher, you'll find out soon enough. At the end of the day, if something is so questionable to you that you feel you need to "clarify" it, JUST DON'T DO IT in the first place. Your little voice is usually correct; listen to it. That is the essence of good decision making and responsibility. Anything else is pushing personal limits or simply engaging in attention-seeking behavior.
Sorry for the rant, but sheesh!