Ben Hallert wrote

With this in mind, I would guess that most schools, upon learning about
the restrictions, passed on them because all those aspiring airline
pilots wouldn't be interested in wasting time with inline multis.

Basically, I'm guessing that safety benefits of an inline are
overshadowed by the practical usefulness of the logged time towards an
ATP (in the eyes of the schools and students, a significant market).

The F-4 Phantom II pilots returning from Vietnam with a centerline thrust
rating didn't seem to have a problem finding airline jobs. :-)

Bob Moore