A supplement to my theory of the Bend of Time being the point of least resistance:
The party can only access the Bend of Time after the following events:
1) Serge takes on Lynx's body.
2) Serge (as Lynx) is sent to Sprigg's dimension.
3) Lynx, Sprigg, and Harle cross from Sprigg's dimension to Home.
It's possible that the Bend of Time appeared in Home due to a violation of a "Conservation of Dimensions" theorem. Lynx's party crossing to Home was the first instance of dimensional crossing that didn't involve a "Missing Piece" (unless Sprigg or Harle qualifies) so this may have caused the availability of the Bend of Time. On the other hand, it could have been Harle or Sprigg that caused this. Harle, as a dragon, may not have been intended to use this type of portal. Sprigg may not even be native to our dimension, or even compatible with it. Whichever the case, this dimensional cross may have violated the "Conservation of Dimensions" theorem. Then, when they finally went to Another, they violated it again, and the Bend of Time became available there.