This was true in the broadcast era, when producers, writers and actors were able to react in real-time to feedback. (For example, Marty Crane was softened significantly in the first season of Frasier after everyone realized he was way, way too crusty and antagonistic.)
When it comes to something that's already completely in the can, like the Frasier revival, it isn't true.
And this revival is garbage. It's trying way too hard to re-capture the Frasier / Martin dynamic, and Kelsey Grammer is playing ... well, himself. The writing is insipid. You could title the show "Dad!" and it wouldn't lose anything.