There is zero chance that Apple doesn't have MacOS and iOS running on RISC-V in the lab.
They did that with x86 and Arm half a decade before any announcement about a switch, not to mention a number of other ISAs that didn't make it to shipping (e.g. M88k) and probably ones that word has never leaked about. IA64, anyone?
They're too large and rich and risk-averse to *not* do it.
I do wonder, which of the two of us actually worked for years in Apple’s kernel team? :)
Not me for sure. I have no idea about you. Of household name companies I've only worked at Mozilla and Samsung R&D. And SiFive if you count people in threads such as this.
I could of course be wrong but I think the publicly known history sets the pattern pretty reliably for the speculation.