Well the GM can be wrong. They can be too conservative, especially if something surprises them (it's my experience that GM's really, really, REALLY hate surprises). And no, you shouldn't interrupt the flow of play, but if it could result in player death, well, can you really wait?
I don't think anyone wants to wait an hour so the DM can retcon an event which shouldn't have happened. I actually had this happen at an AL table, we were running the Curse of Strahd tie-in and I was playing a Yuan-Ti. Volo's was still new, so people hadn't really noticed the Yuan-Ti's benefits yet (they were still lighting forums on fire about "stat penalties in my 5e!? Preposterous!").
So we have to fight, I don't know, I want to say Ghasts. Either way, they had an aura that poisoned you. I was trying to save an ally, and I decided, ok, it's worth me using up spell slots, I'll attack and Smite a Ghast.
So I roll, hit the AC, say "I do xx damage" and the DM stops and says. "You have to roll with disadvantage." Now he didn't tell me why, so I was like, ok. I missed, and everyone was like, you should have waited to know you hit before you used Smite.
I simply responded, "I don't know why I had disadvantage."
The DM replied "you have the poisoned condition".
"I'm immune to that", says I.
"No, you're immune to disease and poison damage, now let me finish this encounter."
We lose a player and I ask if I can bring something up to the DM. He's like, ok sure.
I show him that I'm immune to the poisoned condition, and his response was. "Wait, what? I thought you were immune to poison damage!"
After some conversing with the other DM's, he ruled that the dead player "miraculously survived", which led to suspicions that they might be undead, revived by the Dark Powers!