It’s very hard to provide what coaches, fans, etc., call “consistency,” in a play where, literally, every play is unique. And there is general agreement that PI is among the hardest calls to officiate, at every level. There are 6 categories of DPI, and we are taught that if you can’t fit the action into one of these 6 categories, keep the flag in your pocket:
Playing through the back.
Hook and turn.
Playing the man instead of the ball.
Grabbing the arm.
The cutoff or arm bar.
Early contact.
Speaking specifically of “tangled feet,” the philosophy is well defined. If the players are running even with one another and they tangle feet, no foul. If the defender is in the trail position and they tangle feet, it is only a foul for DPI if the receiver is looking for the ball and the defender isn’t. If neither is looking for the ball, it’s never a foul.