Agree with Chris. I don't know what else you wanna see from Stowers. He hits lefties. He's been remarkably consistent (900/850/910/890 monthly). Defense is fine by all accounts.
Manipulating service is the only other thing that makes much sense anymore. I don't think you need to do that with him. Also you would be getting 3 months (August/Sep/April) of play if calling him up and only 6 months (all of 2030) if you delay. I'm in favor of manipulating when you're talking about 2-3 weeks versus a full year, but he's ready now and you could get significant run out of him in 2022 that could help you and help him.
I won't complain (at least not much) if he's up a week from now vice today or two weeks ago. But I don't get it and if he's not up at all (and would surely be held back to begin 2023 in that case) I will complain about that. That's pushing roster manipulation too far.