No They can't. ARM is not open source, you can't fork it.
And Apple perpetual licence is only for Arm v8 ISA but v9 is around the corner...
Technically, you can fork the development of an architecture. AMD and Intel microcode are not bit for bit equivalent with each other since there are still edge cases where each of their implementation can produce a different behaviour depending on the situation ...
Apple has a hidden AMX instruction set on their in-house processors that are NOT standardized elsewhere on other ARM CPU implementations that they mostly keep under wraps behind a compiler. I don't think you can grasp the ramifications behind competing standards or fragmentation if you think Nvidia can somehow monopolize ARM market by forcing other vendors to negotiate on unfavourable conditions ...
I don't think the other megacorps who are also members of 3GPP will take too kindly to being bullied by another megacorp that couldn't even figure LTE technology. They'd rather a scorched-earth policy where no new ARM extensions get standardized such as ARMv9 or SVE/SVE2 and do their own custom ARM extensions rather than outright hand a victory to Nvidia ...