TLDR; 1.16.1 Possible Fix Described
I'm glad I found this as I don't like to torch spam in single player and I like to have dark, spawn-proof areas.
I thought I would mention that this didn't work for me in 1.16.1, but I tweaked it a little and it seems to work for me so far. The problem arose because Zombie Pigmen are no longer a thing and it caused the datapack to throw an error into the log since it tries to tag an invalid entity. I don't understand enough about minecraft mods/datapacks, but this caused its main function to fail on all mobs, not just cause an error on the old Pigmen. The multi-block functionality worked and created the armorstand/barrier/particle effect/etc, but no tags were being applied to mobs that spawned within its radius.
I edited mob_tagging.mcfunction by removing Zombie Pigmen and adding Piglins, Zoglins, and Hoglins to the hostile list. It seems to work for me so far!
Just thought I would mention it, in case this datapack could be updated for everyone, assuming it's still relevant and I didn't miss a newer/better version online somewhere.
Thank you for creating this cool datapack!