Manufacturers have the option of producing standards-compliant goddamn hardware! Say for PCIe, even if it's a buggy and quirky implementation but it does support ECAM, you can still expose a PNP0A08 and deal with quirks in firmware (hello Socionext/Marvell/NXP).

> PEP (power management plug-in) in the OS […] ACPI spec allows a manufacturer to do this

Doing management in AML is almost the whole point of ACPI. Microsoft pushing this PEP thing into the ACPI spec is bad. This is the "letter" of ACPI now, unfortunately, but it's very much against the original "spirit" of ACPI :/