It's because of
age. I have no clue why you discount that when talking about players, but it's entirely relevant, especially when you're comparing a 21yearold in his 3rd year vs. a 24yearold in his 3rd year. One was considered NBA ready who spent 3 years at college, while the other was considered a raw 1 and done prospect. Both prospects are athletically gifted, so yeah, I do think age is the main factor.
Following the lines of age, look at Jerian Grant vs. Emmanuel Mudiay. Who would you say has the higher ceiling? Both are in their 3rd seasons.
Grant 22.7mins: 8.3pts/4.8asts/2.5rebs/0.8stls/1.2tos on 42.9/35/75.2
Mudiay 19.7mins: 9pts/3.3asts/2.3rebs/0.6stls/1.9tos on 39.3/33.1/75.2
Grant is 25 and Mudiay is 22. Would you hold Grant and Mudiay to the same standard? Would you expect both players to be on equal footing by year 3?
OR would you expect Grant to adapt to the NBA quicker? Why is this? Who has the higher ceiling long-term?
If WCS can put up 18pts 8rebs on 45%+FG, 30%+3pters (on more than 2 attempts) next year, then I would have no problem giving him big money(of course this comes with the assumption that he no longer has motor issues). If he were only 22, I'd give him the MAX, no questions asked.
I think you're discrediting Gordon a lot. There are only 7 other stretch PFs who put up at least 10pts and grab 7rebs. Compare their overall stats with Aaron Gordon and tell me what you see.
https://stats.nba.com/players/traditional/?sort=PTS&dir=-1&CF=REB*GE*7:FG3A*GE*3
TS*GE*10&Season=2017-18&SeasonType=Regular Season&PlayerPosition=F&Height=GT 6-7&Weight=GT 200
Compare his points, rebounds, blocks, assists, FG%, 3PT%, FT%, etc. I already showed you a while ago that his 3pt% is lower because he creates a lot of his own 3pt shots unlike most PFs who just catch and shoot. 34.8% is not bad at all. Lauri Markkanen is at 34.5% at 6 3pters a game. I doubt you have a problem with him shooting that many 3s. His numbers are on par with the rest of them.