M3 Pro Pro Warranty Repair - Need to wait 30 days?

Sometimes when a new model is released, replacement parts can be in limited supply for several months. I have also seen limited parts supply when a particular part has a higher than average failure rate....rare, but I have seen it a few times over the past 20+ years (I have not heard or seen any such issue yet for this model).

FYI, I have seen boot loop issues a few times with the Intel Macs recently (2018-2020 Intel T2 Macs) which I resolved by reinstalling macOS over top of itself (I think it broke due to an OS update patch snapshot issue). I also had some boot issues with the M-series Macs which required some tricks to resolve (had to DFU firmware Revive, and clear NVRAM using the command line, and even reinstall macOS over top of itself as well). I'm not saying your issue could be solved like this, but I do know it took me a lot of time & effort to figure some of this out for my organization's Macs. Most techs I know don't tend to go through the effort required.....the M-series Macs are very hard to work on & troubleshoot. Every time I made an attempt, I had to go through the lengthy process of yet another DFU firmware Revive since I only got one chance each time to try something.

As for the long estimated repair time to receive the necessary parts, you will need to check with your local consumer protection laws to see if you have any recourse.

If there is no part available it seems reasonable that you will have to wait for the repair until the part is available. With respect to the law, consult local authorities. We users in this global community do not know, nor can we state your location local law.