I have to agree with BPF. Field selection and circuit management is a whole bunch easier coming down at 120 fpm than at 800 fpm.
And, glider pilots can and do have outlanding accidents, sometimes fatal.
You can get your glider license without ever having done an outlanding -- or talking to ATC
. In fact the Bronze badge, which most clubs require before turning you loose for your 50 km cross-country is a post license exercise.
So it does not surprise me that BPF's licensed glider pilots required more teaching for PFLs. A PFL requires a lot to be done in a short time while outlandings are usually leisurely affairs.