Honestly, I would like to know the last game that had over a quarter of its points scored from the line. That statistic is baffling.
It actually happens reasonably often.
It has happened 69 times this season.
To answer your specific question, before Thursday night, it previously happened on Wednesday night.
GSW/SAC 284 points, of which 75 were from free throws.
On Thursday, it happened in both the MIL/PHI game (54 out of 200) and the UTA/DEN game 65 out of 218).
There were 3 games this season where free throws accounted for more than 30% of the points (and the UTA/DEN game tonight came close).
Just for trivia, I couldn't find one where 40% came from free thows, but 1 game came REALLY close, and if you wanted to round to a whole number, it would be 40%.
Back in 1997, SAS@UTA, final score was 87-80 and of the 167 points, 66 came from free throws, so 39.52%.
Take Care,
Bart