You are describing specifically "embedded junk" (which includes the M1, sorry Apple) not literally "anything ARM based". SBSA-compliant platforms boot with UEFI+ACPI, using fully generic DSDT descriptions for PCIe (ECAM) and USB (XHCI). Speaking of GPUs, quite common for them to have QEMU in firmware to run the x86-compiled EFI GOP driver straight from the card's ROM and get video output before the OS.
It's cheaper to use custom ARM boards than it is to build hardware that is SBSA-compliant, so consumers can expect that most, if not all, of their ARM devices are not SBSA-compliant.
