You’re right, it’s stupid.
Offset language doesn’t work the way you think it does though. His money is 100% guaranteed, so if they cut him, they still have to pay him.
BUT, with offset language, if they cut him and he signs with another team for $X, then the Chargers have to pay him $X less. He will still definitely get paid the amount of his contract. But if there were no offsets, then Bosa could actually get
more money by playing bad and being cut (he’d get paid by the Chargers, and then also by the new team). Offset language makes it so he gets paid the same as if he weren’t cut.
It’s all guaranteed.
Bosa wants either
1) To be able to "double dip" if he gets cut, getting paid twice, or
2) All his money now so that he could in theory invest it a few months earlier and get extra interest on it
That’s literally all he’s holding out for, and yes, it’s incredibly stupid, and it’s why this is the longest rookie holdout ever under the new CBA, because no one else would think that those things are worth starting so much BS over.