It's entirely possible, though not outright stated, that Worf started the episode in an alternate universe/timeline from the time he crossed the expanse or a bit afterwards. The ending even hints that this was the case, as the only change that seems to be from the main one was the fact that the surprise party happened in that one.
It is outright stated that he ended up in quantum flux while on the shuttlecraft. He was already in a parallel universe when he lands, which explains why he had a party at the start but did not in his native universe.
The star date is the same as the one stated in the Deep Space 9 episode "Sanctuary," which aired on the same week.
The final alternate reality Worf ends up in, the Enterprise has a Cardassian helmsman. This is a reality where the Bajorans are on the warpath after overthrowing the Cardassians, so it stands to reason that guy is this universe's equivalent of Ensign Ro.
