OKC was 5th-To-Last in attempted FTs during the season.
They gave up the 4th most defensively.
I think this whole thing is blown out of proportion a bit. SGA this season was 228th all time in free throw attempts, 230th in attempts per game.
And maybe more importantly, there doesn't seem to be any sort of abnormal jump in attempts from regular season to playoffs when comparing him to other top players:
SGA - 8.8 FTA in the regular season --> 9.2 FTA in the playoffs
Brunson - 6.9 FTA --> 7.8 FTA
Haliburton - 3.0 FTA --> 3.4 FTA
Murray - 3.7 FTA --> 4.0 FTA
Mitchell - 5.1 FTA --> 9.9 FTA
Tatum - 6.1 FTA --> 6.8 FTA
Brown - 5.1 FTA --> 6.0 FTA
Butler - 7.7 FTA --> 7.3 FTA
Edwards - 6.3 FTA --> 5.8 FTA
His attempts have actually increased at a slightly lesser rate than the average player, so while you'd have to compare usage rates and a handful of other variables to make this a more exact study, you'd think it would show up in this data if he were indeed being officiated differently than everyone else.
Of course, it could just be that, based on my limited research, Edwards is getting a bad whistle, which makes it stand out more when SGA is officiated normally. But I'm more inclined to believe that SGA living at the line is more a result of him settling for threes less than other star players.