Hey everyone,
I ran into this same problem when I went to take my FOI test. In AC 61-65E, there is an endorsement for the "Fundamentals of Instructing Knowledge Test." Additionally, in Subpart H-"Eligibility Requirements" for Flight Instructors Other Than Flight Instructors with a Sport Pilot Rating, 61.183, it states:
(d). Receive a logbook endorsement from an authorized instructor on the fundamentals of instructing listed in 61.185 of this part appropriate to the required knowledge test.
However, both the endorsements and 61.185 make no reference to the person needing the endorsements in order to take the knowledge test. For example, in Subpart E- "Private Pilots," it clearly states:
(d). Receive a logbook endorsement from an authorized instructor who:
(1). Conducted the training or reviewed the person's home study on the aeronautical knowledge areas listed in 61.105 (b) of this part that apply to the aircraft rating sought; and
(2). Certified that the person is prepared for the required knowledge test.
Additionally, the Private Pilot Endrosement: Aeronautical Knowledge has a section that states:
I have determined that he/she is prepared for the (name the knowledge test).
The way I understand it, then, is that Flight Instructors are required to obtain an endorsement stating that they have received the required FOI training, but they do not need this endorsement in order to take the test.
Side note: I was worried and went ahead and got the endorsement before I took the knowledge test, however, I was never asked about it. In fact, the proctor even asked me, "You don't need an endorsement for this test, do you?" It was never an issue on the checkride either, so I would not worry about it for the knowledge exam.