Haven’t started reading it yet, but its out now!
Ah, I missed the fact that the lvl19 ASI specifically is allowed to break the max of 20. Yeah, that’s a weird interaction. They just need to change it so that it increases both your score and your maximum by +4.
I don’t think what you said would make it work with Giant belts though, they just set your strength to be that number, you’re not supposed to be able to boost beyond that number.
So, Hammer of Thunderbolts says,
“While you are attuned to this weapon and holding it, your Strength score increases by 4 and can exceed 20, but not 30”
Crawford has stated that the Str boost from the Hammer works with the Giants Belts.
If we utilized a similar wording with Primal Champion then it should work with the other Str/Con boosting items.