My comment about offset language being standard was a reference to NFL contracts more broadly, not necessarily to a player in Bosa's position. I didn't say that offset language was standard for the third pick in the draft, I said it was standard in general and I stand by that based on everything I've read.
A sample size of three is pretty much worthless (really, two, because Bosa hasn't signed a contract). 32 (or 31) is better, but that includes all first rounders and I agree with your idea that higher up first rounders are a better comparison. Hence, top 10. Not an optimal sample, but it's hard to analyze this perfectly. Outside of the top picks, offset language is pretty much universal from what I've seen. If you want to, we could say that as we approach the top of the draft, the probability of offset language being in a contract goes from near 100% to around 50%, but there's a giant margin of error as we get higher up in the draft and the sample size shrinks. I don't think we have good enough data to determine what is market practice with these contractual provisions for a top 3 pick with any real confidence (we do have good enough data for first rounders and mediocre data for the top 10).
Chargers may well be being mocked by others, but I don't see how Bosa is doing himself any favors here. The best way to get a big contract in the future is to actually show up and play. I understand not wanting to be pushed around as a matter of principle, but losing a year and falling in the draft (who knows, he could get hurt in that year too) if nothing gets worked out is a bad position to be in (plus if he falls in the draft, he'll have less leverage in negotiating these provisions anyway).