i believe the entire snake-building in a temple was never intended

I believe the entire snake-building in a temple was never intended. They just needed to program the temple in a way that it doesn't fully fall apart when a few rooms get removed. And the medaillons were intended to safe a few valuable rooms (and not an entire long snake of rooms).
The entire temple would then be much more dynamic: there can be tier 3 rooms with good rewards, but those can be lost the next run. Intended progession could be like this: build towards architect and a few good rooms along the way -> unlock reward chambers -> clear reward chambers and if possible the queen, if not possible kill the architect again -> temple resets after queen kill -> start over
Of course there would be the alternative of building a large temple as an alternative playstyle, but it would not be so easy to get so many high reward rooms as it is right now.
Personally I find the "dynamic temple" playstyle more fun, because it keeps me building and optimizing the temple on a per run basis. This could be made more interesting like having to choose out of an offer which rooms to build and which not. The temple encounters could also be improved: while the vaal enemies and minibosses are fun it first, it feels repetitive after a while due to encountering the same enemies and minibosses over and over again.

You believe wrong because Jonathan and Mark said in an interview they wanted the temple to get bigger and eventually be this big huge thing. So it was intended, maybe not as a snake.