AMD is small though. I have no data to back up my gut but anecdotally I feel like they don't have the manufacturing capacity to keep up with Apple's demands right now.
AMD represents about 2/9 in Windows and 3/10 in Linux of processors using Steam month-by-month and raising; In this same survey Windows represents 95% and MacOS 4% of computers.https://store.steampowered.com/hwsurvey/processormfg/
I think they can manage the production to provide for all Apple CPU needs.
And the game consoles show that AMD can put together a secure, x86 chip at high volumes at leading nodes.