I don't think this sounds so surprising at all. Sounds like Chaves had concerns about the direction of the program, like so many here have posted about their own concerns over the course of this season. If he really does have a standard post-season meeting and Berry came in with "we're almost there, just a few bad breaks, just gotta keep doing what we're doing" plan, then Chaves might have decided "ok, it's time to make a switch".
I'm not saying that's what happened. But reading that story and thinking about what he said, this is extremely plausible.
Remember the old saw "The simplest explanation is the most likely".