I have owned several F-1s, both old and New, an FTb, and an EF.
Regarding Canon's claim that no MLU was necessary with the New F-1, I was just the opposite from David. I believed it until I read an article in Modern Photography back in 1983 or 1984 about this very issue, and they showed photos of a test target taken at long exposure times with the old F-1 using its MLU feature and the New F-1. The difference was much more than negligible. They concluded by recommending the old F-1 or even the FTb if one was doing macro or long telephoto photography.
I will never forget that article. Shortly after reading it I bought an FTb because it was part of my plans at the time to engage in both macrophotography and long telephoto photography. Not long after that I bought my first F-1 (an old one) because I found I really needed interchangeable focusing screens, which the FTb doesn't have. I have used the FTb's and old F-1s' MLU capability on many occasions, and have always been glad they were available functions.
As it so happens, I never bothered using my New F-1 for high-magnification photography (honestly, I didn't own it very long -- a great camera, but I just liked the old one better).
About the EF -- it is most definitely not "mechanically the same as an F-1 in this specific regard" unless David mean specifically the MLU mechanism. Otherwise the EF was unique to all other Canon cameras of the time, possessing a vertically traveling metal blade focal plane Copal shutter (think Nikon FM/FE). Even with the new shutter design, though, Canon decided to keep the MLU capability. Smart move IMO. And not a smart move, IMO to have dropped that feature with the New F-1.
Finally about the OP's original request for info. To my knowledge, Canon has never made an FD-mount SLR that has Aperture and Shutter priority AE as well as MLU. Apparently, however, it is possible to retrofit the T-90 for MLU. I don't know anything about the procedure, I just know that it has been done. Thus, if all three of these features are essential, I would recommend a T90, and then find someone to modify it for MLU.