Do you really not understand or are you just acting in bad faith now? I thought the point was pretty clearly stated...
Does, say, your RAM run at 3.3V or 5V? It doesn't on even rather old PCs by now.
PSU is not providing that actual voltage, whichever it currently is for you. How do you think that voltage is derived?
So if those regulators are not fed with 12V currently, why are you so dogmatically opposed to them being fed with 12V instead? A few cents per mobo extra for higher spec'd components? As opposed to significantly higher savings in PSU?
USB 5V does run on 5V, and M.2 does just run on 3.3V or 5V supply depending on the keying.
These do not have their dedicated VRMs and is on very modern motherboard out there. So you will need to add extra components for them.
So shifting the goal post to RAM doesn't make sense.
The whole point of this 12VO standard is supposedly for efficiency. 12V in theory means it runs less current for a given power.
To minimized power lost on the power plane you want to do the 5V / 3.3V voltage conversion as close to what you are powering as possible.
Ideally you want have somekind of VRM for each of those M.2 slots etc.
All that is skipped is the sight power lost from the PSU cable, and that is insignificant compare to the motherboard traces' resistance.
What you end up doing is the extra "PSU" is just on the edge of the motherboard running through the higher resistance traces to the components you are powering.
Which likely have additional VRMs anyways, as vreg/ripple of PSU itself may not be tight enough to feed components directly with PSU output.
NVME and SATA drives are designed to be fed directly form the PSU and have quite a lenient range for voltage input.
Every PSU worth a damn have tighter voltage regulation than required.