Geno,
I took a quick look and found three things.
1. Lee did not actually shoot their 7.5 MAS data, they took it from some other cartridge. See the top of each page on the 7.5 MAS.
2. Lee cut off .300 Savage data at 45,000 psi, the MAS at 40,000.
3. And maybe I shoulda been explicit on this, I used the starting loads for .300 Savage and only the 150 grain bullet. Dunno that I worked up any, but I may have. I ain't such a fool as to start off with top data for any cartridge.
As you point out, the current Lee manual has data. Might as well use it.
I did not have such a resource so I used what I had to find a starting load. Worked out fine and I'll do something similar the next time I run into a cartridge I don't have data for.