It’s not generic – the duration of blockstun, even if tuned in lock-step with active/recovery frames so that advantage on block remains the same, affects gameplay in various ways, e.g.
- The feel of the move.
- Confirmability on hit: if there’s enough recovery on a move then the attacker can know when it has hit and confirm with another hit on reaction, otherwise to facilitate a confirm they may need to take a risk or press a button they mightn’t want to press if the first move is blocked.
- Whether an opponent can take back their offensive turn on reaction if the move if negative and blocked. Shago’s surge divekick is negative now – it used to be +7 or something like that – but it’s fast enough to where it’s difficult to pick out and check Shago on the other end of in time. If a move is negative but fast, and could’ve been a positive move instead, it can be difficult to identify the move and make an offensive move after it, or it may require a guess or an option select.
- How easy it is to punish an unsafe move on block. For a while, TJ’s flying knee recovered so fast that people weren’t getting the punish on reaction for blocking it.
- Frame traps imparting varying amounts of blockstun can make it difficult to reversal out of pressure, but can also open up various option selects, e.g. pressing a button to participate if move A is used, but so that your input is swallowed in blockstun if move B is used.
You can determine blockstun for a move by adding the active and recovery frames together and subtracting the advantage on block.