My hybrid sounds better than when I got it. But then, so do I. Which is chicken and which is egg? It's mildly interesting to me, but honestly since I plan to retire with this bass, it's also moot. I think of a relationship to an instrument as being a bit like a marriage. You learn how to interact with your spouse over years based on daily experience. Has the bass itself opened, or have I acclimated to the subtleties of the bass? Something has opened. Maybe one, or the other, or both. Beyond that, I'd rather just play than worry about it.
I can honestly say the same about every instrument I've ever played, including piano and French horn. The same arguments could be made about those as well. For me, in the end, if warming up makes the result sound better, it makes sense to warm up, but not so much sense to try to find an answer to a question that might not be empirically answerable. I guess that makes me agnostic yet again!