alt Hacker NewsAs with many things, "It's complicated" but effectively, yes
Such system firmware is generally provided by AMI / Insyde / Phoenix and similar.
There are a few vendors who decide to go their own way (notably google using a fork of Coreboot for their chromebooks), but it's generally list of vendors that you can count on a single hand.
If it means anything I'm pretty sure AMI provides A/B updates on most products i've used with their stuff.
But that's always been the case. Phoenix and AMI have been the dominant BIOS providers for over 30 years. Both have always provided modular tookits for OEMs to customize their own ROM images, write their own ACPI tables, etc. UEFI gives even more control to the OEMs. If Framework isn't doing that properly, that's on them.