You haven't seen an example where a player's second contract was paid with the assumption that the player would "grow into it?" I think if that's true it's missing the trees for the forest. I think our whole perception of what makes a "fair" second contract already includes the bump for potential. Like Wiggins was maxed because Minny thought he would eventually become a non-negative player. Jamal Murray was maxed out because the Nuggets believe he'll go from solidly above average to being a legit star. Not every second deal is like Jokic, Derrick Rose or Kawhi where guys are superstars or already have hardware to justify their deals even if they didn't improve substantially.
I'm not trying to say that production doesn't matter at all. The lack of production is why we aren't debate a max extension for Murray instead of $13M or $25M per year. But I believe young players are usually signed more off narrative than anything else. Murray's narrative is stronger than his NBA history (something for which he's gotten praise and criticism on this board for years now). I think his actual value to the Spurs is higher than PGs who've changed teams this year because their previous clubs didn't seem to want them badly enough. In that same way, Jamal Murray and Pascal Siakam both got maxes more because their teams did well last year than because those guys put up elite statistical production.
I think the best comp for a Murray extension might be Aaron Gordon. He had a strong narrative going for him despite not having a lot of production (13/5/2 with negative impact stats on a TS% of 53). The Magic gave him a $76M/4 deal. Under a 2020 cap, that projects to be around $86M/4. Schoder's extension in today's money is $82M/4. I'd be okay with Murray getting something like that on an extension, because even he he doesn't live up to it, it wouldn't be a horrible deal to have lying around. I'd be elated if you were correct, because that might be the best extension since Curry's. And I'm not all that bullish on DJM, but I can't ride with the idea that he should be content signed a long-term deal with the same APY as Danny Green.