Ha, it's funny, because I'm the one who mentioned before that I always assumed Irina wasn't a long-term illegal, and my most recent rewatch only made me more certain that this interpretation is correct. I had a whole list of reasons why, most of which centered around the fact that the episode seemed to portray Irina as the love Philip left behind, not someone who moved forward with him on a parallel track. But while I was reviewing the episode just now to get my thoughts together, I stumbled upon what to me seems like a much more concrete reason to think I'm right:
"Your life in America -- is it a full life?"
"Two -- a boy and a girl. You?"
"I was married." "Divorced?"
"Yes. A son."
If Irina were a deep-cover illegal, the marriage they're talking about here would be to another officer, just like Philip's marriage is. So why would Philip's first assumption be that they got divorced? Wouldn't "died in the line of duty" or "was recalled to Moscow" be a much more probable way for such an arranged marriage to end? Indeed, when Philip suggests to Elizabeth in the next episode that the two of them could get divorced, he presents it as a new option that they would have previously considered unthinkable. The only way it makes sense for Philip jump to that conclusion with Irina, it seems to me, is if her late husband was a real one she married back in the motherland.
Also, Irina's explanation gets very complicated if she's talking at one moment about her cover husband in Canada and then in the next about her and Philip's son being raised by her parents back in Russia. It goes beyond a lie of omission into confusingly cobbled-together fabrication in a way that it doesn't if she's talking about her late husband in Moscow and the boy they raised together there in between her temporary international missions.