AB350m not getting bios updates while Pro 4 does

There could be any number of reasons why one board model gets an update and another does not. Most commonly however is because they use different power designs/controllers. If the update only changes the way power is handled then it would only apply to the board it was released for. I suspect this is the case here. The Pro4 uses a beefier power design. Other, common changes, will always see updates released across the platform.

Edited by Xaltar - 11 Jan 2018 at 2:06pm

Power design is 2 part, physical hardware and firmware  To differentiate between a cheaper and more expensive board there may be options on one that lack on the other, despite largely identical hardware for those functions. There is often also differing supporting hardware with lower or higher tolerances that mean settings need to be different between the 2. Power design differences is just one of many possible reasons that warrant an update on one but not another though.