Are they really the best shooting backcourt in history?
You can definitely make an argument that they're the best shooting backcourt in history. Curry set the single season record for three pointers made with 272 and the duo combined for 483 between them, shooting an impressive 42.9% from behind the arc. The Warriors guards launched an average of 14.1 threes per game, making over six a night.
They're clearly a talented pair of shooters, but are they the greatest shooting backcourt ever? There are lots of different ways to analyze shooters: FG%, 3P%, TS% (True shooting combines points, field goal attempts, and free throws to determine overall shooting), and ppg are just few of the quantitative tools out there. In the end it comes down to opinion and the totally subjective "eye test" but these and other numbers can give some insight and help validate or undermine Jackson's claim.
In 2010-11, Kevin Martin and Kyle Lowry quietly had terrific shooting seasons. They were the first and third leading scorers for the Rockets, tallying 37 points per game (compared to Curry/Thompson's 39.5) and shot a combined 43.2% from the floor. The Rocket guards shot over 300 fewer threes over the course of the year and their 3P% of 38.3 and 37.6 are good, but not quite Curry and Thompson good. Their true shooting percentages, however, are better than the "greatest shooting backcourt in history". Martin's was 60.1%, higher than Curry's 58.9, and Lowry's 55% was higher than Thompson's 53.3%.
Six years earlier, in 2004-05, Steve Nash shot 43.1% from beyond the arc and Joe Johnson shot an incredible 47% from long range. The Suns duo combined for fewer points than Curry-Thompson and Martin-Lowry, but their true shooting percentages of 60.6 for Nash and 55.6 for Johnson and combined field goal percentage of 47.8 suggest that these two were more efficient than the other pairs.
If you care about field goal percentage, look no further than the most dynamic perimeter 1-2 punch in history, Michael Jordan and Scottie Pippen of the Bulls (yes, I know that they are not technically a backcourt pairing, but Scottie played plenty of point-forward and, come on, just work with me here). In 1996-97, for example, they shot a combined 48.1% from the floor and scored 49.8 points per game between them while hitting on 37% of their three-point attempts. Jordan finished the season with a of 56.7 TS% and Pippen had a 55.4 TS% of his own.