Also a lot of the rhetorical devices used in grime were borrowed directly from hip-hop. From heavy punchlines, multi-syllabic flows, cadences, rhyme schemes, to storytelling, these skills were imported from the US. UK MCs would still be spitting on garage without the US influence
And yes there was crossover which is why I said it’s a parallel influence and not a direct linear one. Americans would argue its linear. Grime was already moving (Eskibeat, 2step) before it took influence from hip-hop. UK drill is definitely a sub-genre of hiphop tho.