I don’t know what you did, but in one single game I had 2 bugs with Auriel’s knockback. The first was when I pushed Yrel in her jump into a wall and she just ignored the stun. The second was when I pushed Malfurion through a Leoric entomb.
Getting pushed away while a movement enhancing ability is still playing out is something common and is not really considered a bug, however I’ve not experienced a situation where it would not stun the target when you use Detainment Strike on such target under same condition. From my experience, Diablo’s charge will reliably stun a target like Muradin that is jumping, if he carries him to the wall. Diablo can also reliably be stopped mid charge by Detainment and will get stunned against the wall as well if he gets pushed far enough, though I’m not excluding the possibility of isolated cases based on travel distance in offensive direction, I’ve just not seen any so far.
As for Entomb, did you by any chance use the talent which pushes away all the enemies in a line? This tends to happen when hero models overflow the small space within the walls and are subject to forced movement. Recently there was a similar report where Diablo’s charge would push out a target to the outside of Nazeebo’s zombie wall rather than stunning it within against the ring. These issues appear very technical in nature and would require hero radius adjustments, which would affect the game balance as well, but are just rare enough not to become consistent and predictable.
Well, Nazeebo’s wall is just a bunch of summons. A trapped ETC for example can push them all away with W, so they are not a true wall that could be smashed against.
Force Wall however is impassable terrain and can be smashed against with Shadow Charge.
It was just malfurion in the entomb and I did not have that talent, it was almost like he was pushed through the back corner.
True wall or not it still does count as an object with collision for the duration (buildings, terrain) and hostile units can be stunned against it from either outside or inside. Entomb might as well be made of a similar objects hidden to the player that could unknowingly be subject to dislocation by certain effect, otherwise when someone slips out they follow the rules similar to that of newly spawned unit that has not received a rally command on the way out of a production building, and the spot that the hero will get pushed out to is nothing but random.
Considered a bug or not, looking at past experiences I would say it is an engine limitation. Playing around with it might break some other things.