Its not LVFS. Its that our BIOS does not support self-updating the ME firmware.
For the system to update itself, it needs to have the updater for that specific firmware built into the BIOS that is already on it. 11-13th gen have only ever used external updaters for ME (whether that’s the Windows, Linux or EFI version of it).
It seems FW will update ME via its own capsule, if they provide that ability. A separate capsule for most firmwares. Just like each ReTimer has its own capsule, plus the main BIOS. On Core Ultra, ME is the 4th capsule.
Other manufacturers rather pack all firmwares into a single capsule and let the BIOS manage all of the separate parts internal to it, because that makes it easier to control all parts of the update at once. But that really does not change, that the updater needs to be already present in the BIOS to do that.
We do not know if they only provided half of integrated updater-functionality at first. And only got to doing it in later generations or some other reason (although I think that is probable, given how extremely resource constrained the updates have been). Also seems to be a toolflow problem for FW, as they claimed this ability was present since 13th gen device. But then, for the single official update they launched, they still did not use it and shipped the ME update with the external updaters.
LVFS involvement is that it only supports a limited amount of update protocols. Updating ME directly is not one of them, because every manufacturer does that as part of the BIOS and via capsule if they use LVFS at all (because capsules are OS agnostic and the most sensible way for any core firwmare). Also, BIOS version and ME firmware are tied together, which is why manufacturers want to update this together as part of the main BIOS update.