It, uh, it works like fuzzy defense guys. during blockstun you get one option, outside of blockstun you get another.
The standard way to deal with fuzzy defense is to bait the non-blockstun option with a gap + your option to beat it. They choose DP, you leave a gap and block the DP or make it whiff, they choose a mash you leave a big gap and let the mash whiff or stuff it, etc.
Fuzzy defense is just a thing in its own right you're going to deal with. Somebody is going to be fuzzy mashing you in every game, that is life. The alpha counter OS is no different, it just adds the alpha counter to it. It'll be useful depending on how often you want to alpha counter things while calling out other mix up options. Seems pretty specific and hard to implement to me but it probably has some pretty solid use vs certain situations.
Edit: What does make this one pretty neat is that the option you choose during blockstun is actually not block. I guess with SFV coming it would be a good idea to make a universal write up about how this works to explain "this will all exist in SFV and it's not that scary."