Since it says Spiner "called," it could be either: we don't know whether he said it verbally or wrote it down.
As someone who did acting to finance college...
I can confirm the sterotype which is:
Never act with children or animals.
Sad, but true.
Kids: they need decent parents. But parents shoving them into the spotlight? Well, that's not fair at all.
Animals: They always do what you expect them the most: Do what ruins your shot! :D
That's a very Brent Spiner thing to say, doesn't mean he actually hated that cat. And it wasn't just one cat playing the role anyway. Most if not all of them were good cats I'm sure.
I vaguely remember reading an interview about this though, Brent was saying the cats were terrible for not staying where they needed to be and their scenes always took ages. I don't think he hated the animals, but the resentment was real.
I've seen him make these remarks in some documentaries - I think - and it comes across as a joke.
If I spent 7 years playing my character as a boy, only to suddenly become female for the sake of a single episode where I get pregnant I'd be pissed too.
Spot was classically trained and had doubts about the seriousness of the project, so there were a few ego clashes early on
I will say at less the actor for spot had a good time. He runs around with his tail sticking up.
They bring in Commander Maddox to cross-examine Data.
"Did you accuse the plaintiff of only taking direction if eating tuna was involved?"
"I did."
"And do you think this is true?"
"I do."
"And you don't feel sorry at all for saying such a derogatory thing about one of your co-stars?"
"I do not."