Apologies - looks like after reading the thread in reverse order you
and I are on the same team (at least I think so).

Mostly. I don't have your faith in examiners or inspectors to
determine that too many corners have been cut. I've seen too many
substandard instructors breeze right through the checkride. I really
don't think the right things are being tested. That's why I don't
think much of off-site one-week or two-week CFI training programs.
They're quite effective at getting people the certificate, but not so
effective at producing a quality instructor. That requires extensive,
one-on-one training and mentoring (here we're very much on the same
page). It also requires that you start with pretty good material -
meaning someone who is already a competent soaring pilot and has some
aptitude for instructing. I'm not saying every instructor has to have
flown the diamond distance, but surely flying the silver distance ought
to be considered a (very) minimum standard.

300-400 hours is actually quite a bit in gliders, in most cases,
whereas in airplanes it's actually not much experience. That's not
really so much a function of the aircraft as it is a function of how it
is used by most pilots. For a power pilot, 200 hours of XC usually
means 180+ hours of droning along, straight and level, in good weather,
with little effort or thinking required. Maybe there will be 20 hours
in there of flying challenging weather, terrain, etc - and maybe not.
It's not because it has to be that way - even a power VFR XC can be
challenging if you're, say, crossing the Rockies in a low powered
airplane (and it actually requires some soaring skills) - but few power
pilots do that kind of flight. Most power pilots don't even launch on
a XC flight unless they are reasonably assured that they will complete
the flight to the destination effortlessly. Soaring is different -
making destination is never really certain (even if you don't land out,
you often have to scale back the task to fit the conditions - and we
all accept that you may land out anyway) and you're constantly working,
looking for lift, working lift, replanning what you're going to do.
200 hours of that makes a pilot. That has certainly been my experience
when I have taught glider pilots in power.

Can you realistically make a glider instructor out of someone who has
400 hours of nothing but flying circles around the home field (if you
could find such a one)? Of course not, but you could easily get him to
pass a CFIG checkride.

Michael