Did commercial glider pilots used to give instruction?

I read recently that in 1996, the regulations were changed
so that commercial balloon pilots (who used to
be able to give instruction) could no longer do so.
They were instead required to become balloon CFIs.

As far as I know the only current reference to instruction
given by non-CFI or ATPs is the "psuedo-instruction"
given by towpilots to wanna-be tow pilots. As far
as I can find, this is the only non-CFI/ATP
flight endorsement in part 61 and 91.

I also heard rumor that
commercial glider pilots used to be able to give
glider instruction to students. Is this true?
How long ago did this change?