A bat summoned within a large enough volume of light blocks completely loses movement AI.  However, it seems if there is an air block within range they can navigate out.  Though it is most likely known by players that light blocks are not air it is almost certainly unexpected that a bat would not be able to path to this.  This unexpected behavior can directly affect map creation.

This was replicated by filling a 50 x 50 x 50 volume with light_block with tiledata of 15 and then summoning a bat at roughly the center. The bat will hoover in place.