Ah, you just plain dislike DA, that's fair. I don't believe the difference between Lavine's and Ayton's maxes would be "nothing" (it never is when you're building a contender and the margin of error/salary shifting gets closer and closer) but also don't have the actual numbers to compare, I'm no capologist.
I think it's less about PATFO being "comfortable" with Zach's knee, and more about the situation overall. I'm not fine with that knee, lol. Especially not with his history and another (granted, a debrilement, not a repair, but still) surgery already lined up, before we get to see him play again. And as you say, it's wholly different scenarios between S&Ts and outright signing either player; but on a vacuum, I think Ayton is clearly a step above Lavine as far as "FAs to go after". I just don't see the argument against DA, that you also can't make about ZL (not the #1 option on the team, not really worth the max, etc).
Lavine's shooting is definitely elite - but that's not what his game is based on, is it? Would you pay Lavine the max to be a spot-up 3pt shooter, if his knee was bad enough that he couldn't blow by defenders anymore, and couldn't penetrate to score nor dish out assists? no. That's my concern. Maybe not next year, not immediately, but down the line; and I say this with the knowledge that the Spurs, as-is, simply aren't ready for a le run. Not next season and probably not the one afterwards, either. That definitely matters when you're picking out the core pieces of the will-be team, and is a big reason Ayton >> Lavine, IMO at least.