Maybe, just maybe, the laptop variant is N3B without the fusion and then Desktop will be N3E with the fusion. That is possible explanation why the release was all in one go back in October.
Very interesting, and would make a lot of sense. No need for an interposer on a laptop. It takes a 16" chassis to adequately cool ONE of those chips - an Ultra laptop would look like a 2" thick Alienware gaming monster, and have the battery life of one, too.
If you add a second interposer to the desktop chip, the Mac Pro chassis suddenly makes sense. It alone has the space, cooling and power to handle a 4-way interposer.
You then have:
M(N) - iPads, MacBook Airs, low-end MBP, Mini and iMac. Performs like a decent midrange PC. ($800-$1500).
M(N) Pro - High-end Mini, midrange MBP, new midrange iMac?. Performs like a performance-oriented business PC or a high-end laptop. ($1200-$2500).
M(N) Max - High-end MBP, low-end Mac Studio, new high-end iMac?. Fastest laptop in the world, performs like a top-end desktop PC or entry-level desktop workstation. ($2000-$7000).
M(N) Ultra (2x Max) - High-end Mac Studio, iMac Pro????, low-end Mac Pro? Performs like a powerful desktop workstation (midrange to upper-end Threadripper or Xeon). ($4000-$15000).
M(N) Extreme (4x Max) - Mac Pro only. Performs like a VERY high-end desktop workstation. May outperform any single Threadripper or Xeon. ($12000-$35000).
That's quite a line.