it isn't as though
It isn't true or correct that; it is not the case that. Usually used to point out a misinterpretation or misperception. I'm just holding onto the funds until the company's new account is set up—it isn't as though I'm going to keep them for myself! It's not as though she couldn't handle the work herself. She's just being lazy!
it isn’t as if/as though
, it’s not as if/as though
used to show that a particular explanation for something is not the correct one: It isn’t as if he didn’t recognize me! He just walked straight past me as I stood there.