Basically, when you get to the boss room in The Hollowed Lair, strikes bounties stop counting progress. I don't know if it's with all bounty types, but I've particularly noticed more often that the Weekly Bounties which require you to kill enemies with a certain damage type on strikes were stopping at the boss room. It's pretty frustrating when you have 149 kills with solar, get to the boss room and, after killing 294219 enemies, end up with 149 still. I've been bumping on this issue even many months before Beyond Light, so I believe it's something that wasn't addressed yet.