We need more RAM

Yes, an M2 Ultra chip can only have up to 192GB of RAM, but this Unified Memory Architecture and is different to how it works on an Intel chip. It's supposed to be more efficient, and Apple Silicon certainly feels faster than Intel chips.

Have you evaluated how much RAM you need for this project ? Or do you just want the max possible (to be future proof). Clearly intel based was flexible to upgrade RAM which M series are not at all.

Well, my colleague naively assumed that since it was up to 1.5 TB 5 years ago, and modern servers could go up to 6TB (if not more) — then modern most powerful Mac Pros would be configurable to up to a few TBs at least. Apparently he assumed wrong. Unified memory (that's for quick GPU - CPU transfers?) shouldn't be important in his use case as he is interested in CPU only.