It's like the MB manufacturers lost the point of the B series boards and even AMD's marketing (B550 Enables PCIe® 4.0 for Everyone) is kinda out the window, unless there are more boards on the way at the sub-£100 mark that is.
As for B450, it's an option. Just not one i thought i'd have to be looking at right now lol. Although the prices of those these days are about the same as a good B460 so..