This is an example of an offensive foul for making contact with a defensive player in an unnatural manner. Offensive players may not extend any part of their body into a legal defender in an effort to draw a defensive foul. On this play, the defender is clearly going to miss the shooter who then extends his leg out to draw the contact. While it is the defender who makes contact with the offensive player’s leg, this is an offensive foul.

This is an example of an offensive foul for making contact with a defensive player in an unnatural manner. Offensive players may not extend any part of their body into a legal defender in an effort to draw a defensive foul. On this play, the defender is clearly going to miss the shooter who then extends his leg out to draw the contact. While it is the defender who makes contact with the offensive player’s leg, this is an offensive foul.
https://videorulebook.nba.com/archive/offensive-foul-shooter-kicks-out-leg-into-legal-defender-2/

Harden and Paul and D'Antoni have spent the last 4-5 years pushing the extreme edge of the rules (gaming the rules) for a competitive advantage. The last 4-5 years the referees have allowed the experiment to flourish in the regular season but cracked down on it in the post-season.