[AkibaSilver]

Another problem might be that this was all written without much knowledge of how the Build finale was going to go, depending on how much the writer share between each other. Ex-Aid's been over for a year now (and doesn't have multiple words deals to confuse things), so it might be easier to tie together.

Also, I've put together a theory of how all this timeline shenagin stuff works out. To me, this makes the most sense.
SKYWALL WORLD 2017 - Heisei Generations final occurs, uniting the two worlds for a bried time. This is what allows Zi-O to cross over, and is where the Build portion of Episode 1 occurs.

SKYWALL WORLD 2018 - Build finale, which dumps Sentou and Ryuuga inti...

MAIN WORLD 2017 - Because Sento and Ryuga have to be around at this point, per episode 2, as they fight Kaijin Rider Build. This is where the creation of KaiRide Build occurs, and his defeat, in a time loop. Sento and Banjou, because their powers have been stolen by Zi-O, are affected, morphing Sento back into Takumi mentally, and reverting Banjo;s character development. However, it doesn't change things fully, probably because (as Den-O showed) time is hard to change - even if their past has been infected by an evil Kaijin Rider, the two are still friends.

MAIN WORLD 2018 - In some looping timeline, where KaiRide Build lived, he gets blown up by Geiz. This restores the timeline, allowing Sento and Banjo to regain their memories, and give Sougo the Ride Watch which he only gives them when KaiRideBuild is destroyed, which hasn't happened yet because he doesn't have the RideWatch and KaiRideBuild is still around, and oh dear I've gone cross-eyed.

Basically, the best I got is that the Another Watches don't do anything specifc, they just pervert the timeline. I'm basing this off the Eighth Doctor novels, though, so don't blame me if it doesn't make sense. Those don't make sense either. God, I hate time travel.