Of course, you will need a BIOS update to enable Rocket Lake-S support. Whether all 400-series motherboards will get this update is unknown. Some manufacturers may opt to exclude some models, especially lower-end boards.
While it's possible to enable Rocket Lake-S processors on all LGA1200 motherboards, we suspect that support will vary from one motherboard vendor to another. Besides the shift to the Cypress Cove microarchitecture, one of Rocket Lake-S's biggest attraction is PCIe 4.0 support. Nonetheless, some vendors might not have initially purposed some of their 400-series offering to support PCIe 4.0, especially the entry-level motherboards. That could be the explanation of why Biostar didn't mention Rocket Lake-S support on non-Z490 motherboards.