Shakespeare didn't specify the amount of alteration, did he? My point is that Jack's love is true in that when he fell in love with Irina, he didn't fall in love with a college professor or whatever she was pretending to be, but with her--her essence, or whatever you'd care to call it. It's a transcendent sort of thing because whatever happens--time, circumstance, realization that your basic understanding about the beloved one is false, etc.--love doesn't waver. But for Jack it's potentially tragic because he had the misfortune (assuming that Irina is evil, of course) to fall in love with Irina in this way.
-_-