Which is probably what happened.
It wasn't intentional, but I like it that it's fuzzy.
In Muse, that playwrite is writing about how Tom Paris is kissing both of the Delanney sisters at the same time.
And I'm thinking "Dude! That's you're boyfriend he's turning into a porno slut! Stand up for Tom's virtue for frakks sake!"
Although it seems that the real world writer, Joe Menosky, might have forgotten that they were together, or didn't believe that they were still together because no one had done a Tom/B'Elanna getting it on episode in a while... Or it's possible he didn't watch episodes he hadn't written and therefore had no idea they were glomming.