While we don’t know for sure, water probably makes up something like 0.05% of earths mass, which is not that much at all! And in fact, you can easily acquire this much water by only accreting the driest types of planetary building materials (eg enstatite chondrites) without needing any contribution from the water-rich bodies discussed in this article. Though, these water-rich bodies almost certainly did deliver some fraction of earths volatiles!