Hoglins can't seem to pathfind/jump properly over snow as show in the picture below (when attacking and facing N or W.).

To replicate make a wall (preferably a longer wall because they can occasionally jump over in the corners) 1 block high and place snow on top and on the ground 2 blocks out (if there is no show on the ground they can jump over) Then summon a hoglin using command /summon hoglin ~ ~ ~ {IsImmuneToZombification:1b}