So do the startup values in the game account for this? As in if a normal reads 7f startup I can beat -7 moves because the data is done with the "extra frame" accounted for?
Block advantage in the game is calculated based on the assumption that you are not doing a reversal. Startup values have nothing to do with that calculation.
If something is -7 on block, then the defender is free to act for 7 frames while the offender is in recovery. The -7 assumes that you are
not shaving off 1 frame of blockstun with a reversal.
So if you want to punish with a normal, you will need to use something with 6 frames of start-up. This is simply because a 6 frame move does not become active until the 7th frame. There is a misconception on TYM that a 6 frame normal should hit you in 6 frames, and that's where the "extra frame" myth got started.
The only reason you can punish something that is -7 with Tempest EX spin is because it's a reversal, so it shaves 1 frame of blockstun, therefore making the move -8 instead of -7. So in reality, you are punishing something that is -8, with a 7 frame special.
The only thing that is changing, is blockstun, which in turn affects block advantage. Start-up values are not affected at all.