Not likely, even if most humans couldn't fight them in hand to hand combat, technology was advanced enough at that time that humans could be a threat (think robo, grobyc). That view of lavos's behavior is also assuming that lavos is sentinent.
It wouldn't be that much of a stretch that lavos could have evolved with this as an instinct. That whenever a lavos is ready to birth lavoids, that it clears life on the surface to give its broodlings the highest chance of surviving to fly off to other planets.