The answer is the exact same for gliders and powered airplanes. Assuming no other change in configuration, less head wind means higher ground speed, or more forward distance at the same descent rate. Hence, you land further down the runway. To compensate in a powered plane, you reduce power; in a glider you pull more spoiler.
thats what they were saying - but I don’t think it’s that simple
starting point - just turned final , maybe 500ft agl / 55kt IAS and all is stable with ie 20kt head wind - so in theory about 35kt groubd speed
as you sink w 1/2 air brakes - the wind drops to 0kts - remember the AC has the Kinetic energy of 35 kts - this would be stall already in a twin Puchacz w 2 big guys
as such would need to convert Potential energy into kinetic to bring speed up to 55 kts again = dive !!!
remember also that old formulas about acceleration of a mass ( takes time )
...... I calculated if started at 500ft where wind drops out , you would need to drop to 400 ft just to regain speed !
practically speaking - I noticed all the guys landing short on the strong wind day, and the curved slope of the runway made the wind drop off at about 300ft
my good luck was I saw them, and on the next flight aimed further down and surprising just barely passed the threshold
—— so something is not adding up for me