Was just playing Standard Bo3 playing Jeskai Control vs. an Esper mill deck. I won the first game on my upkeep with the burn from Jeskai Revelation with zero cards in my library. Sideboarded and won game two as well, then the game sent us to sideboard again and we played a game three. I know I'm not misremembering because my sideboarded cards were already in my deck (like my two copies of negate) when it sent us back to the sideboard for the third game. I also double checked that I didn't lose the first game despite casting the burn on my upkeep, because when it sent us to the third game the opponent didn't have a game win either. First game just got deleted.

I don't really have screenshots because it was timed so I just played the match.

My guess is that because Jeskai Revelation also has a draw two effect that would've killed me the client just bugged, but I'm pretty sure the burn is supposed to go off first because it's first on the card. Ended up winning the third game anyway but I was low on time and pretty scared lol.