I don't think the Rio Grande cared much about which tender went with each engine. The #315 had at least 4 different tenders over the years. The K-36 tender with the squared off coal bunker was on three diffrent engines before C&TS days when it saw a 4th.
It looks like when an engine was shopped it was turned out with an appropriate tender. If it came off a different engine, that was fine. Thenders did seem to stay on the same job some times though. A couple of the Durango switchers had the liitle tender with the headlight shelf.