I disagree that it's a "thought-terminating cliche" - it certainly shouldn't be. There's a difference between trusting someone, versus using them to your advantage but having an exit strategy.
I agree entirely that there is value, sometimes significant, in exploiting the ecosystem created by a larger fish. You'll see that in my comment, wherein it says:
... leverage off XXXX to
start with ... be able
to shed [it] and replace
it with something else.
You are saying the same thing I've said, but emphasizing that
starting in the jaws of a larger fish is sometimes worth doing, and sometimes they'll deign to let you survive there.
Consider, though. If you become successful - which is surely your aim - then you will come to their attention, and they will do whatever they like.
So I repeat: Don't trust them. Use them, yes, but don't trust them.