I don't see any reason why what is clearly a continuity alteration like this can't redefine how we view the show's in-universe reality. When I saw the Borg infant, like everyone else, I assumed it meant they reproduce, but if someone comes along later & redefines what I saw, I'm not so closed off to reject that new take, & dismiss it as "Oh, it's just a show, & we shouldn't expect to make sense of it"
That's why boards like this exist. So we can come together and do that very thing. I was fine with Riker seeming to know they reproduce, when he said it, but if later it's stated more concretely that they don't, then I'm also fine reassessing my interpretation of that scene, & now thinking Riker may have just been speculating, & perhaps the baby was assimilated. If that helps us make better sense of the overall show, what's the harm? Sure, we won't be able to have it work out that way with every example, but in this case, it's fine
It's a discussion board. If people are going to get bent out of shape over us speculating, for the purpose of providing ourselves with a more defined viewing experience, then folks who are taking it too seriously are the ones trying to shut down our fun. Hell, some of the best fan fiction only exists to fill in those blanks in the very same way. It's perfectly healthy to do it