You think that's going to motivate him to sign? It's not like the NHL where you can trade him. Given what the offer is, it looks like he simply doesn't want to play there. Refusing to report to the team that drafts you isn't as unusual in the NFL as it is in hockey, especially if the franchise is poorly run. Now they're burning the bridge even further.
Bosa's not innocent in all of this but the Chargers can't afford to let a top draft pick like that just walk for nothing.