Lenders use EFX 5, TU 4, EXP 2. Those are considers Mortgage FICO scores. They do Not average scores they use the Lowest middle score when looking at all borrowers. An example if you have two borrowers with scores of 677, 701, 724
And a second borrower 505, 585, 605. The score used would be the lowest middle score 585 would be used in Pricing and all rules set by a particular program.
These 3 Bureau scores can be obtained on this website and are exactly the scores 99.9% of all lenders use.