Yes, more weird than that. x86 PCs have fairly standardised boot and autoconfiguration (UEFI and ACPI). ARM based systems, including the Apple M series, don't. You just have to know what's there (device trees), and Apple isn't going to tell you. Hence why it's difficult to make another OS run on it, because you first need to find out what hardware's even there, and how to talk to it. It's initialised by Apple before iBoot runs, sure, but you don't even know what it is, so good luck writing a driver for it.
The Intel ME / AMD PSP are creepy, and probably a security risk to the device owner, but they're not weird, you can run an OS without even knowing they're there, and they like it that way.
Asahi Linux already does use an open source UEFI implementation (U-Boot) to boot Linux.
https://en.wikipedia.org/wiki/Das_U-Boot
The Asahi installer will also allow you to install UEFI alone, in case you want to use UEFI to install some other OS.
The hardware management engines in modern x86 chips are backdoors running at a higher privilege level than the installed OS's kernel.
It's hard to see them as anything else.