Noticed today (2024/04/25) that Rylak’s deathrattle does not trigger some of the battlecry’s during battle, or triggers them once, then nothing.
The following battlecrys did not trigger during battle (from Rylak):
Discover tavern spell - rodeo performer (tier 5 card)
Discover minion of a type you don’t control - reef explorer (tier 4 card)
Same happened when Rylak’s deathrattle was passed onto the fish of nzoth - that deathrattle also didn’t trigger neighbouring battlecry from the above minions.
So far I was not able to test this mechanic with other minions, hence listed only 2.