Because in a turn the inside wing is flying at a higher
AOA than the outside wing, the inside wing will likely stall, and
drop, before the outside wing. I understand that in some gliders
without the newer wing designs this inside wing stall may well be
followed an eye-blink later with an out-the-bottom spin entry.
Actually, this is a common misconception, but there is no such thing as an
inside wing stall on any turn, unless it is a very shallow turn in a
pre-stall configuration, and the pilot suddenly applies aileron opposite the
turn, in which case the inside wing will stall first.

This is the common situation when pilots are trying to prolong the glide by
holding the nose high and doing skidding turns.
The opposite aileron is the only way to prevent the wings from banking more
(which is what the pilot is erroneously trying to prevent).
That is why, it is repeated so many times, by so many people, so many books,
that you can't spin from a steep turn, only from a shallow turn.

The "Pooch" may be such a glider.

I don't know where you got this from. The Puchacz has absolutely marvelous
characteristics.
I spun and instructed in them for years.