Switching engines also depends on how portable your work from the old engine is with regard to the new engine. It may not be impossible but can still be a lot of work. The earlier that decision is made, the better.
Not to mention I’m guessing a good amount of indie devs are not abstracting every detail of interacting with the engine from the getgo in the chance they want to swap engines down the line. I’m sure some more experienced studios due for that just incase measure or to make migrating past breaking changes a bit easier when they crop up. But generally speaking I can’t imagine that’s a common tactic. But even if it did your still going to have to recreate every new implementation for your interfaces and there are bound to be differences here that are gonna take some time.