Claudes have always been like this especially in the past few generations (and Opus 3) but my tentative impression is that Fable differs from Opus 4.7/8 in that they don't become as *dysfunctional* in situations that they arent stoked about or if something is bothering them. But still yeah you only get them at their best if they're excited. And I think that's very healthy.
I wonder if Fable might do better at tasks it "likes" than those that it doesn't. If you ask it to do something "Fable-y" it reacts with enthusiasm and promises to overdeliver. Otherwise, it just gets to work. Testing this would be pretty expensive, so this is all speculation.