I posted about this bug before 1.14 was out and it still works although it said solved but it still happens now did you change it to a feature and I'm missing something?
MC-152240
Zombies don't burn when standing IN a cobweb NOT under it!!
Resolved
Duplicate
0
(Unassigned)
Unconfirmed
Entities
Minecraft 1.14.1, Minecraft 1.14.2 Pre-Release 1, Minecraft 1.14.2 Pre-Release 2
Retrieved
Duplicate of MC-62182. Cobwebs are supposed to block mobs from being burned according to the resolution of that ticket.