e.g. they do seldom if ever take patches for adding support or fixing issues in older boards. They just sit there ignored.
A fork or entire new project with different focus is sorely needed.
There do exists individual users that work on newer stuff, after the MSI Z690-A / Z790-P there were 2 people that did ports for H610 since at that point the platform was supported and they only had to port the Motherboard. However, they are rather rare, since the kind of user that Coreboot seems to attract are from the privacy and security anti-ME/PSP crowd that don't even want to use newer platforms, which is the exact opposite of my view.
A lot of the work companies does may be just for their internal systems or reference platform and these may not get to the hands of end users, ever. I still recall Phoronix articles covering Coreboot releases always taking a jab at the new supported Motherboards until the MSI Z690-A DDR4 port from 2022.