Thing is that I’m fairly certain that spires, giant blossoms, etc function in the same way as other “queen” enemies, so they do in theory serve as the focal point for the fungus, in gameplay terms as well as how it should work in-universe. It’s just that they can replicate even without an existing “queen” entity in the area, counteracting the normal behavior where killing the leader ensures their eventual extinction.
However, given the spire and related fungal bosses give off a ton of spores, it does mean that they spread slower without the extra production the spire puts out, but they can still grow faster than whatever effects despawn leaderless creatures (like giant ants without a queen ant, for example).
The same thing can happen with blobs. Even if you venture into a slime pit and kill the brain blob, the blobs will keep dividing anyway.
