> continents won't have fossils if they are under frequent bombardment. Right, but if giant bombardments completely boil away the oceans and atmosphere to rai

> continents won't have fossils if they are under frequent bombardment. Right, but if giant bombardments completely boil away the oceans and atmosphere to rain liquid rocks back down on the surface, there very very likely won't be life, either. So the claim is not just that "fossils only go back to X" but that X is so close to the end of the giant bombardments that there's almost no time left (geologically speaking - maybe 10-20MY) for "life but no fossils yet".