During Korver's all-star season with the Hawks, he shot an insane 49.2% on 6 attempts per game over 75 games. Similarly, Redick shot 47.5% on 5.6 attempts per over 75 games and Joe Harris' 20-21 shot 47.5% on 6.4 attempts over 69 games.
Other seasons to consider:
Novak 11-12: 47.2%, 5.2 attempts despite only 19 minutes per game, 54 games
Duncan Robinson 19-20: 44.6% on 8.3 attempts over 73 games
Kapono 06-07: 51.4% on 3.1 attempts, 67 games
Kennard 22-23: 49.4% on 4.6 attempts, 59 games with two teams
Buddy 22-23: 42.5% on 8.5 attempts over 80 games
Nash 07-08: 47%, 4.7 attempts, 81 games
Joe Johnson 04-05: 47.8% on 4.5 attempts, all 82 games
Klay 14-15: 44%, 7.1 attempts, 77 games
Ray Allen 01-02: 43.4%, 7.7 attempts, 69 games
Reggie Miller 96-97: 42.7%, 6.6 attempts, 81 games
Kerr 89-90: 50.7%, 1.8 attempts, 21 mpg, 78 games
Lillard 19-20: 40.1%, 10.2 attempts per game, 66 games
Harden 18-19: 36.8% on a ridiculous 13.2 attempts over 78 games. Only season ever with 1000+ attempts, pacing Curry's 15-16 by 142 attempts
Eric Gordon 14-15: 44.8% on 5.2 attempts over 61 games
A couple shoutouts to guys who had standout volume/efficiency for the era:
2003-04 Peja Stojakovic. At the time, for the standard 3pt line (not shortened like '95-'97), his 240 3s made was the most in a season and 43.3% was barely behind the Ray Allen season mentioned in the OP for highest 3P% with 200+ made. And he put up that career-high efficiency while being thrust into the #1 scorer role due to Webber's injury.
1988-89 Dale Ellis. He wasn't the only player to surpass the previous 3pm record that year, but it took Michael Adams nearly 130 more attempts to make only 4 more. Ellis shot 47.8% from downtown on just over 4 attempts per game while putting up a career high 27.5ppg.
And just a little fun fact: In 1983-84, Darrell Griffith made 91 3s for the Jazz. No other team in the league made 80+.
The idea of a player scoring almost 28ppg, hitting almost 48% from 3, yet only taking FOUR 3pointers a game is so wild to me