Build a wall of glass and throw snowballs at it: you'll clearly see they go right through as if the wall weren't there.
Same happens with eggs, ender pearls, bottles o enchanting, and thrown potions.
Comments

Dupe of MC-93607
Perhaps, but if so this is a better explanation of the bug than that is.
I'll tell them to update their ticket. Congrats! You were picked.

Very likely caused by the fix of MC-73884


Looks like it's fixed in 15w49b; not sure why this is marked 'fixed for 1.10'

It looks like they did revert the fix for MC-73884 in 15w49b. My guess would be that they left this open because their 1.9 development branch still has MC-73884 and they only removed it from 15w49b to not have snapshots with such a crazy bug.
As for "Fixed in 1.10", it was momentarily closed that way (I'd guess that was just an accident of some sort) and apparently the "fixed version" field doesn't automatically get cleared when the bug is reopened.

This bug has returned for 1.13. Eggs dispensed will go through glass and the chickens will also sometimes lose ability to move or be pushed if they spawned right next to a wall.
Dupe of MC-93607