The premise of the connector is that it attaches to the board in a similar way as soldering the chips (the LPCAMM connection interface is directly on the back of the chips) but uses compression instead of solder to make the electrical connection, so the traces are basically the same length but the modules can be replaced without soldering. There is no reason you couldn't use two modules to get a 256-bit memory bus. It sounds like AMD designed Strix Halo to assume soldered memory and then when Framework asked if it could use CAMM2 with no modifications to the chip, the answer was yes but not at the full speed of the CAMM2 spec.

CAMM2 supports LPDDR5X-9600, which is the same speed Apple uses in the newest machines:

https://www.micron.com/content/dam/micron/global/public/docu...

The Max chips have a 512-bit memory bus. That's the one where the comment you linked suggests putting one module on each side of the chip as being fine, and there is no M4 Ultra or M5 Ultra so they could be using LPCAMM2 for their entire current lineup. The M3 Ultra had a 1024-bit memory bus, which is a little nuts, but it's also a desktop-only chip and then you don't have to be fighting with the trace lengths for LPDDR5 because you could just use ordinary DDR5 RDIMMs.