My guess is that when Gronk has been on camera before, the producers (I won’t say directors, because my sense is that the things he’s doing are producer-driven) want him to be a big funny goof — a BFG if you will. Put him in a feature film, after some acting classes, some work with an acting coach and a director with a vision, and there will be a much different level of performance. There may be a ton of crap left on the editing room floor, but a good director can shape a performance.
Think of how many comic actors, thought to be nothing but goofballs based on early credits, got into the right role with the right director and turned in bravura serious performances: Robin Williams, Adam Sandler, Jim Carrey, to name but a few.
We do know that for all of the Yo Soy Fiesta Gronk moments, this is also a guy who has, by all reports, been very circumspect with his money, who has the vision to put all his loved ones in a bus driven by a designated sober driver, and according to B.B. and others, does a ton of work to make sure he knows the playbook. He is not some dumb-bunny, See-ball/catch-ball, meathead
Oh, and yes, I have spent over 33 years around professional actors and directors.