This relies on two assumptions, and I don't think either will be true:
1: Zach LaVine is worth more in 1.5 years than he is today.
We know the cap will rise 10% the next two years, because that is the cap raise max.
So 154.6M next year and 170.6M the year of Zach's option.
A 30% max will be 51M that year. Zach will be making ~29% of the cap. It does not seem to me today that people would sign Zach to a new deal at 29% of the cap.
Based on where Zach LaVine's trade value is today, it sure does not look like anyone views him as a 30% player today or else he'd have gotten more in trade value. He has a full season and a half to change that narrative, but it does not strike me that Zach at 1.5 years older is going to be worth a higher percentage of the cap than he is right now.
2: That he can't/won't accomplish the same thing by an opt in / extension. There's a fair chance he gets that done this off-season if things go well with the Kings. This is the lowest risk for Zach to lock in the most money, but even otherwise, I think he'd have looked to do an opt-in and extend next summer unless he felt he could get more money by opting out (back to point #1 about how likely that is).
He's not eligible for supermax, so the most extra he could make by opting out and doing FA vs opting in and extending is $3M, and unless he views his value as likely to fall considerably in 26/27 season, then he has even more upside by waiting for another 10% cap increase.
I think the most likely scenario for Zach is an opt-in and extend though, as I think he's going to be a below 30% guy on his next deal.
Fundamentally, another way to look at it is this:
If Zach were to opt out, that means his value is worth more than his contract, and we probably would have wanted to keep him anyway, and so really a question here is do you think Zach's on a good deal vs bad deal, and if the answer is good deal, then of course you should be disappointed with this return, if think you think it's a bad deal, the option is scary and you should be happy with this trade.
The league seems to have hedged more towards bad deal, but I can see why someone might feel either way based on Zach the player.