It just means they tweaked things while in production. No different that they did with the Cardassias uniforms from TNG into DS9 and all the "facts" made about the Trill in TNG than were all but forgotten in DS9. Same as the implications of Sisko's father maybe being dead to see him alive and semi-well.
It seems slightly different to me. The Cardassian uniforms in "The Wounded" changed because they had more money for "Emissary," which was a series pilot. There's also no reason to assume that the Cardassians simply didn't change the design between episodes.
The thing about Sisko's father is simply fans making an assumption based on a line of dialogue that later turned out to be false. Sisko never said he was dead, after all, just spoke of his father in the past tense (something he would do even after we saw that Joseph was alive).
The Trill were totally a changed premise, but one that was done at the outset of
Star Trek: Deep Space Nine because (1) the original make-up would have looked horrible on Farrell and (2) the story restrictions of no transporting would have been limiting to the format, without any story benefit. They really should have just chosen a different species name, but that was never changed, for whatever reason.
And then on
Star Trek: Voyager...the writers ignored the premise that they set out with in the first place. If it wasn't going to work for the series (or, more to the point, if they weren't going to stick to it) then
don't establish it in the first place. Of course, it doesn't make sense that a ship of Voager's size and crew compliment would be a long-term exploration vessel, because the remnants of that original premise remained in place for seven seasons.