Here are Jaylen Brown's 2nd year advanced stats (since he plays less minutes). 54.7 TS% (50.9 2PT, 37.8 3PT, 58.8 FT), 9.3 RB%, 8.0 AST%, 1.6 STL%, 1.0 BLK%, 11.9 TOV% with a USG of 20.6 and a PER of 12.6.
Brown actually doesn't show much improvement in many of those categories from his 1st to 2nd year, which is much diferent then Green who took a pretty big efficiency jump from year 1 to year 2 in pretty much all of those categories (which again is unlike Brown).
There’s a context that you’re ignoring, though. Jaylen went from getting 17 mpg to playing twice that many on a good playoff team. Meanwhile, on both raw numbers and a per possession basis, he improved every single stat except blocks, despite playing against starters and expending energy as an elite defender.
I didn't ignore that context at all.
Per 36 Brown year 1
13.8 p, 5.9 r, 1.7 a, 0.9 s, 0.5 b, 1.8 t, 3.8 f - 20 of 78 games started
Per 36 Green year 1
13.4 p, 6.1 r, 1.9 a, 0.7 s, 0.8 b, 2.5 t, 3.2 f - 52 of 80 games started
Per 36 Brown year 2
16.0 p, 6.2 r, 1.8 a, 1.1 s, 0.4 b, 2.0 t, 3.3 f - started every game (54 thus far)
Per 36 Green year 2
16.2 p, 6.5 r, 1.9 a, 1.0 s, 0.4 b, 2.2 t, 2.5 f - started every game (78)
As I've been saying nearly identical stats. They also have nearly identical roles on those teams (at least in year 2). Sure, Boston was a better team than Seattle/Oklahoma City, but the similarities are uncanny from a role, production, etc. stand point.
And don't get me wrong, I'm not suggesting Brown will level off like Green did, but Green wasn't the first or last person to not show much growth (I mean look at old friend KO for another guy that didn't show much growth in his game). Look at Myles Turner from the draft before Brown. Great 2nd year with nice growth from year 1 to year 2, but a major regression this year. Maybe Turner doesn't turn it around and year 2 was his best year. Then again, maybe Brown is like Jimmy Butler, Giannis Antetokounmpo, etc. that show tremendous growth every season.
Obviously only time will tell on which way Brown ends up, but the comparison to Green thus far is pretty spot on given their actual roles and their actual on-court production (not personality wise, but production wise).