You can't price match Black Friday pricing at Best Buy, not sure if you can anywhere for what matter. If you can, then people will buy weeks in advance based on leaked deal info and just go in for a PM.
My local Best Buy has let me PM Black Friday deals for years, going as far back as when I used to work there in 2000-ish.
Every year I do exactly what you are warning against. I go in on Tuesday or Wednesday pick up what I want then price match sometime on Friday afternoon. A few years ago I made out huge, got over $2000 refunded to me.
The only price match limitation I've ever run into is on the door buster items which they won't PM at all. Granted, a new release like that may end up as a DB item rather than part of the overall BF sale.