Yes it certainly can be done, but there's a cost and design complexity with doing that too. I did a quick count of gimlet (our server sled's) power rails and got to over 26 different power domains, and I probably missed a few in my quick scan! It's unclear to me if the efficiency gains from re-doing these with something more exotic to go from 54V would make enough of a difference to justify doing so, and we'd still end up with some stuff like the SVI2/3 controllers needing an intermediate rail (or have to go design those ourselves too) and some analog rails needing LDOs for noise rejection reasons etc. As mentioned before, creepage and clearance at higher voltages cascades into layout complexity and pain if you have to run it everywhere on the board: but for the same reasons we're talking about this, we can't very well do a 54V:1V conversion in the back of the sled and run it all the way to the front- losses, noise etc.

As with all things engineering is a series of tradeoffs and right now, an IBC from 54V to 12V has been a reasonable design point for us.