You know what... thinking it through- If "Lovelace" is a different arch from "Hopper", and the first is monolithic while the second is some multi die(MD) thing (insert marketing term) then my guess is this: Hopper is on TSMC 5nm, which has TSMC's new chiplet bridge packaging, while Lovelace is on Samsung 4nm.
Doing the calculations for potential yields on AMD's chiplet GPUs showed just how much cost can drop for doing multiple smaller chiplets over relatively large monolithic stuff. If Nvidia has the ability to do multi die graphics GPUs I suspect they'd prefer that quite strongly over not. Profit margins shoot up quite a bit there, at least potentially. So the reason for going MD on one arch but not both is, so I imagine, you can only do it on one instead of both. If Nvidia expects to sell out its entire TSMC wafer allotment just doing AI chips, then of course it's going to just make AI chips, the margins there are way, way better than for consumer GPUs regardless of MD stuff. So then they have a different node, and foundry, for their lower margin business. One that doesn't currently have the packaging tech for multi die stuff like they'd want to do. But if you're out of options, and everyone around the world is for the near future, you take what you can get.
It's not like Samsung 4nm isn't a good leap from their 8nm. Going by Samsung's numbers density should be over double and power might nearly be cut in half. Caveats of "those are headline numbers" even included, just a straight port of Ampere would see solid benefits across the board, let alone any other improvements. Anyway, that's a possible scenario that makes sense to me anyway.
