I presume the point of the SuperMax is to encourage players to re-sign with their own teams, but it seems like in Jaylen's case the huge spread almost works in the opposite direction. 4/189M is so different from 5/295M. For a guy like Tatum you just pay it, but for a guy like Jaylen it potentially swings from good deal all the way to a bad deal for the team.
If the SuperMax was a more reasonable premium in this situation (say 5/250M), they probably just offer it. But now, if they make that exact same offer (far more than Jaylen can get otherwise) it lands entirely differently because of these artificial limits and they risk Jaylen pissing Jaylen off.
I wouldn't gloss over the future (potential) downside of 295M for Jaylen. If he stagnates, Jaylen could be a negative asset you have to staple 1st round picks to get rid of. It's not a guarantee you can just swap him on that contract for some other disgruntled but very good max guy in a lateral "shake things up" kind of move.
The advantage of the supermax with Jaylen is that because of the old rules on extensions, as a non-max guy his extension amount was limited to a number (120% of current salary) that was just an instant no go. This means they can offer him more (even if not the full $290 over 5) than anyone else, and also they'll know where they are a year out so they have little chance of him walking for nothing (where otherwise they'd either have to trade him now or take the chance he pulls a Kyrie).
Wait, why do you think Jaylen would take any less than a dime of the supermax? If he walks the Celtics are completely screwed so they would be forced to trade him for pennies on the dollar. Either way, they aren't top four team on the East have no real realistic path back. He has the leverage. Also there is not a huge amount of advantage saving the 6.5 million between a max deal and super max for a team over the luxury tax.
1. I really doubt it would be pennies on the dollar, past guys in the supermax type tier have gotten good returns. I think there is little reason to think a Jaylen deal (and the sattelite deals that likely come from it) drop the Celtics out of the top 4 in the East. They were the best team in the league on net, 2nd best on record, and Jaylen's impact on that wasn't nothing, but he's not even close to Tatum in terms of impact, the return for him would likely be enough to make them still a top 4 seed easily. As to why Jaylen would take it... does he want to make more money with BOS or less elsewhere, some guys it's about principle, others it's about making the most money they can, others have other desires (winning, being the guy, where they want to live, who they want to play with), if the Celtics offer him $260 or 265M (so 31.5-31.8% year 1 with 8% raises) he's making $20M+ more over 4 years than in FA, plus has a $60M 5th year option (obviously you give him the option in return for shaving percent off the base).
2. There is a major advantage to saving 6.5-7M starting in 2024 when the 2nd apron and it's punitive punishments come in.
There is a reason a lot of the best cap guys (Marks, Smith, etc.) are saying the new CBA has changed a Jaylen Brown designated vet full 35% extension from a no-brainer to a much more risky/complex decision.
Before we heard about the new CBA rules I thought it was a no-brainer to offer Jaylen the full 35% with 8% designated vet on the theory that you could trade him if you needed, and it's just Wyc's money. But now... less clear. Paying that much for 2 guys is REALLY tough in the new CBA, and trades for big money players will be harder going forward as teams try to duck the apron.
I don't think a full supermax for Jaylen is devastating (barring injury or stagnation/regression) but I do think it's a legit question now as to whether they will/should offer it. I think a lot of teams will suddenly be a lot more careful with transactions where in the past they said "it's just money"