Schoenberg, the closet microtonalist (??)

There's been some discussion again of late (as there is periodically
practically everywhere in the world) of the music of Arnold Schoenberg and,
in particular, of his use of closed systems for chordal generation.

However, is it not the case that Schoenberg was fundamentally a closet
microtonalist? If Harmonielehre is any indication, a work which I read
(unfortunately, since it is uneven) rather carefully, the overtone series
was Schoenberg's ultimate destination, although he ended with the 12-tone
system as the great "temperment" compromise as, obviously, many others have
as well.

As he states in the Harmonielehre (well, OK, so it IS in a footnote):

"Then new systems of temperament with smaller intervals might come about,
later perhaps even complete independence and freedom in the use of all
conceivable intervals, all conceivable frequencies and combinations. Now
the division of the octave into 53 equal parts would be an example of a new
temperament... It is clear that, just as the overtones led to the 12-part
division of the simplest consonance, the octave, so they will eventually
bring about the further differentiation of this interval."

Joseph Pehrson