LEW had it down best - that's what I've been trying to say as well.
There's also the "ITS WESKER'S RECOLLECTION" argument too, but this works just as well.
Capcom didn't "Screw up the RE Timeline" with UC. It was meant to just be an arcade style game, and the only parts that were actually made canon were the single-player stages (the Wesker ones) and the stuff that takes place in 2003.
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