he could have written it : E - FE FE FE - D G. so...what better idea to get than from the master himself. remember, he wasn't seeking to be like everyone else and was probably teaching haydn a thing or two. 'hey, master - look at this - i can also trill from the bottom note.'
Then that would've been trill on E. Somehow Mr. Beethoven wanted the trill on D. Since preceding note is E, according to the rule the trill starts from bottom note. Something tells me good 'old Haydn was perfectly aware of that rule, so that lesson most likely is only result of your vivid imagination.
measures 56, 58, 59 make it MUCH easier to trill from the bottom note (fast triplet) for a beginner student.
Would you with straight face tell me this Sonata intended for beginner students

? Moreover, I highly doubt Beethoven intended such monumental works as his Sonatas for students. I might be terribly wrong, but somehow I believe he was composing MUSIC, i.e. expressing his feelings, experimenting with techniques and ideas, etc., without carring much about intended performers.
As a side note, I believe one should play not the way it is easier, but the way it is right, both musically and stylistically.
But surely, you can stick to your guns, whatever they are.
also, beethoven himself WRITES IN THE TURNS at measure 45. some OVERDO everything and add a turn to a turn.
So what?
What's your point here, what do you want to say, and how the fact some retards overdo everything is related to the current discussion, which BTW, is about TRILLS (not turns, if you still remember)?
make it simple is my motto.
I realize that and believe maybe THIS actually might be the core of the problem.
Unfortunately, I don't have much time to go through the rest of your fantasies.
Best, M