Yep, that.

It will also depend a lot on the plane the pilot is moving to, and how long they've been flying the glider. More stick time is more stick time and helps. In the cases of the students I've worked with, the transition plane was a smaller electric, which compounds the "behind the plane" issue because they had to keep it close to be able to see the darn thing, and keeping a small, faster plane closer magnifies being behind the plane a bit. Landing is also different. Not harder, really, but belly landings with gliders don't require the same finesse with the flair, while powered planes are easier to get into a short runway because they don't keep on going in ground effect like a (non-spoiler) glider will.

I forgot to add, that if you don't have an instructor (or don't want one) or you have time issues with getting instruction, or whatever, then a powered glider is probably the best way to get flying.