Alraiis, I can respect your take on the rules, but I don't think that's the whole story. The books are pretty specific on how DM adjudication based on "what the table thinks makes the most sense" is the primary method for deciding stuff like this.
So yeah, if you want to go "strictly as written", it's reasonable to let it apply to forced movement. Heck, under the flavor interpretation, it can work either way, too.
But taking off my "online rules discussion hat", my interpretation would be "The rogue stabbed the guy in the gut, if he tries to run away he'll rupture... getting moved isn't the same thing as running away" versus "There's a gigantic burning area 5' to the left, if you end up in it from moving or being moved, either way you're inside the fire."
Another way of looking at it: Forced movement has no relation to an NPC's own movement speed, meaning that Walking Wounded -> Thunderwave would work on slow creatures but not fast ones. That seems wonky to me, and when applying the rules leads to something wonky I typically go for another interpretation.
I'm just saying, I think looking at the imagined events going on "in game" shouldn't be excluded from rules discussions, since the rules themselves tell the DM to keep those considerations in mind. I may be an outlier, but I've never had one of these situations come up in play and actually had it slow us down -- typically it's a matter of seconds to reach consensus on how we all think some edge case should work.
Or in other words -- If you're the DM, then you choose. If you're the player, then your best bet is typically to politely go with how the DM sees it, because it's such a small and uncommon situation.
