My understanding is that the split is more superficial than that. The contributor in question (he used to do YouTube videos mainly, no contributions to the firmware) created his own vibe coded app/client and is trying to own the trademark on the Meshcore name. He controls the .co.uk site, the youtube channel, and the discord group. The firmware is still the same, created by the people behind the new .io website.

So the split is just a "the development team has nothing to do with the .co.uk site, his youtube channel and discord group", not a fork.