Question: if a relationship is based on trust and communication, then how is it insecurity when you no longer are able to trust this person due to lack of communication? That is essentially the issue is it not?
The post-op (wo)man failed to communicate a vital bit of biological information to their significant other and the S.O. is expected to what? understand? If they do not understand and forgive (initially mind you. We do not know what happened the next day, month, year down the road after the reveal) they are insecure?
If anything, the failure to communicate this, what should be basic, information to their sig. other shows insecurity on the (wo)man's part, not the other way around.
It's completely reasonable and understandable for the boyfriend to have a complete reversal of feelings towards this person who, essentially, deceived them for x amount of time. Again, we do not have the "where are they now" story and there may have been a level of forgiveness we are unaware of. As far as the initial reactions, completely reasonable and expected.