That's quite disappointing, especially since B650E in particular has everything most people would realistically need, even enthusiasts. Also begs the question of what exactly is driving up motherboard prices so much if these boards can't even handle fairly conservative memory speeds. The socket assembly itself?
Been a while since I looked at motherboard design, but it looks like both of those are 6 layer PCBs. That's not super high end, obviously, but doesn't stand out negatively either. Wonder if there's some instability on the DDR5 training side? Perhaps some firmware tweaks could help? I do think it's important for AMD to keep up the quality standards for the mobo manufacturers if they're going to advertise Zen 4 with these memory speeds.