You're right in a sense that rocks falling out of the sky today are "acreting" to the Earth, but the total contribution to the mass of planets during the late bombardment was pretty small.

Mass scales as the cube of radius. So if the Earth's radius is 4000 miles, then a 100-mile wide (50 mi radius) asteroid only increases Earth's mass by 0.0002% Or 1.4% for a body the size of Texas -- which would be larger than what formed any of the near-side basins on the Moon, and maybe larger than what formed Hellas on Mars. Only a few such large bodies struck after the Moon, Mars, or Mercury formed their crusts, which the Moon at least did near 4.5 billion years ago.

The planets certainly gained some mass between 4.5 Ga and 3.8 Ga, but, they were probably ~ 90% or more of their final mass at 4.5 Ga, so whether that counts as "accretion" or "bombardment", I'll let you choose.