I just wrote a really long reply when I should've just wrote here, anyways, I figured out the solution to my DDR5 XMP settings woes accidentally because it's apparently an issue with previous version of MemTest86. Long story short explained with screenshots.
Note: I have a Z690 Extreme motherboard, not sure which boards it affects as Memtest just mentions Asus.
While trying to figure out why my RAM was always testing bad with XMP profiles or auto settings unless manual manually configured in Memtest, I stumbled upon this warning when checking to see if there's an update.
SMBus controls some power and monitor settings, I guess according to chatGPT. Anyways, I thought it may have been affecting my board somehow aside from just MemTests but they offered a workaround for MemTest to be able to view SPD Info.
Change SPD Write Disable to FALSE, instead of the default setting.
After more restarts than I like and playing with more configs, I found that SPD Write Disable = TRUE does seem to be affecting some settings when they're set to AUTO most importantly it seemed like it was affecting my BIOS because after changing the setting, XMP profiles now work and the Memory Controller Voltage on auto settings would always get set to what the vendor specified (1.1v) which is a little short of what's stable at XMP settings (For me around 1.35v), but with it set to FALSE it seems like the motherboard is able to correctly train the DDR5 RAM during boot and set appropriate settings and timings for anything set to auto.
Hopefully Asus finds a fix, but at least there's a workaround to stabilizing DDR5 ram at the settings advertised without having to do a lot of research and testing anymore.
Advisory: Not sure where the issue lies, but the initial restart might not be enough to train your RAM if you have Fast Boot enabled, suggest a cold boot or disabling Fast Boot for that first restart at least.
Source: DDR5 SPD Troubleshooting
Edit: I'm getting old, posted screenshot of wrong section for first image.