Mobs fall through walls when spawned atop them

When spawned atop cobblestone walls via a spawn egg, mobs will fall through that wall. I expected them to behave as with fences, and remain atop the hitbox.

0Tested in creative mode, and confirmed to occur with all available spawn eggs on both mossy and normal cobblestone walls.

When spawned atop cobblestone walls via a spawn egg, mobs will fall through that wall. I expected them to behave as though spawned on fences/fence gates, and remain atop the hitbox.

0Tested with all available spawn eggs on both mossy and normal cobblestone walls.

When spawned atop cobblestone walls via a spawn egg, mobs will fall through that wall. I expected them to behave as though spawned on fences/fence gates, and remain atop the hitbox.

0Tested with all available spawn eggs on both mossy and normal cobblestone walls.

When spawned atop cobblestone walls via a spawn egg, mobs will fall through the block. I expected them to remain atop the wall's hitbox, as they would with those of fences and fence gates.

0Tested with all available spawn eggs on both mossy and normal cobblestone walls.