Scab grenades create a patch of fire that expands to fill a certain area. In most cases this means a round patch of fire, sometimes other shapes if there are nearby walls. However in a very tight space the fire tends to do weird things, an extreme example of this is the staircases on archivum sicorax. The stairs do not connect to the floor below because they terminate at a ledge to form a one-way drop. When a grenade lands on the stairs it tries to expand but the only way it can go is up creating a 50-foot long snake of fire, this is unrealistic for numerous reasons.
It makes sense for fire to conform to the space around it, but I think there should be a hard cap on how far fire can spread from where the grenade actually lands so you don’t get silly cases like this.