My experience (as an amateur) is different than yours (as a professional). Nevertheless, I disagree strongly with this one point .the elephant wrote: the extremes of both instruments have a way of informing our playing when on the so-called *correct* horn.
In my opinion and experience, it is the notes on the "correct" horn that "inform our playing" when on the other horn.
Remember, for the average player, it is success that leads to more success. Playing moderately high (for me) on an Eb helps me (in your excellent term: "informs my playing") when I switch to a BBb and play the same notes (which are now HIGH...for me). Going the other way does not help (me) - instead, I find myself taking the "tricks" I need to play very HIGH (for me) on the BBb and using the same tricks when playing a note that is more secure on the Eb (and which I can play more easily, with better tone, without the "tricks"). If I play these notes often on the Eb, I find that you are correct - the notes are there on the BBb WITHOUT THE TRICKS.
Now, for a professional trying to get that last note or three at the very, very high end, it might well be that playing high on a contrabass may make you more aware of what the problems are, and remind you to play with more attention to detail - which "informs your playing" when you switch to "the correct horn".
It just doesn't work that way (or, at least not efficiently) for me.









