Hey, that can work, they can be past versions of them that got sidetracked by these new places.
After all, even if they are in, for example, 600 A.D. fighting Retinite, before, while going for the Masamune, there wasn't any Sunken Desert, but after telling the woman in Zeal not to burn the seed, there now is, meaning all past versions who crossed 600 A.D. for various reasons (Looking for the Masamune, going to Magus's Castle, etc.), are now going to see the place. Eventually, they will get Time Bastarded, but still, they can do something that can make a further change to the time line to the ones already done (thankfully they don't, or else more troubles could arrise to keep track of the continuity).
So, it can work, while preparing to fight Lavos, they stumble across these new places, opened by their future versions who defeated Lavos, decided to check them out, but in the end, it's meaningless since they got Time Bastarded after.