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Not necessarily, but there's a bunch of possible discrepancies that you mentioned.
EQ vs EX: An additional tradeline will absolutely change the score for better or for worse.
TU vs EX: The TU version here is TU98, which frankly isn't really commonly used anymore for much. I know some lenders do pull it, but it's somewhat unusual for any national lender to do so. It's likely that any EX score you've received will be either '04 or '08. Walmart FICO, again similar issue with TU08 and I have no idea if theirs is a specific industry option or not... see next point.
EX in general: where did you get your score from? If it was from an Amex application, there's a good chance that it was the Credit-Enhanced industry option on the pull, and that's not the same as what you'll get from here on EQ or TU for that matter, and I have no clue regarding the Walmart FICO.
As a result, it's really hard to pull any sort of comparision with the way things are today: a mortgage tri-pull is about the only meaningful comparision available to us as consumers currently where we know they're identically the FICO '04 model across the board from all three bureaus.
I seem to remember that EX hates balances unlike TU which hates # of CC reporting a balance.
A good rule of thumb would be that anything you do credit wise that helps your TU/EQ FICO score will help your EX score as well.
The only thing you can do EX wise is to insure everything on your EX report matches your TU/EQ reports and vice versa I may add as well.