the mobo vendors that want to will update their "beta bios" to support the new chips just like they did with the most recent 3000 chips.
The boards with 32mb ROM will most likely support all of them. This is a guideline from amd more than anything, if the board partners figure out a way to make it work then it will work, they just wont get help from AMD directly.
Just like Intel/microsoft saying anything on skylake and up doesnt support windows XP yet ASUS is explicitly advertising win XP support for their new Z490 Apex.
They said that x570 dont accept first gen or the excavator am4 APU yet my AsRock board accepts every chip ever produced for am4 and every ram including ECC unbuffered which AMD only supports on "pro" chips, and its the cheapest x570 available.
Im thinking about putting a potato chip in the socket it might boot up.
Honestly the mobo manufacturers probably get tired of tech support calls "why doesnt my chip work" so they just say **** AMD and make everything work.