If the foul was that the defender pushed him out of bounds, would you not have either defensive holding or illegal contact? both of which carry 5 yd penalties rather than spot of the foul enforcement.
Someone else will have to address actual NFL rules pertaining to DPI on a receiver that is, or returns from, out of bounds. I suspect they are the same as NCAA, for which PI rules only apply to inbounds eligible receivers. So, while OB, a receiver can't be "interfered," even if forced OB. If he was OB voluntarily, but returns inbounds, he is still not eligible, so he still can not be "interfered." If he was forced OB, then returns immediately, then he regains his eligibility and PI rules apply.
In the play in the NFC game, the ball is already in the air when the defender drapes himself over the shoulder of the receiver, while the receiver is still inbounds. That's DPI. The defender's contact then causes the receiver to step out of bounds. The ball passes by and lands immediately thereafter, so the receiver didn't really have an opportunity to return inbounds. But, that's moot. The PI occurred earlier, while both players were inbounds.
Should DPI be a spot foul? Or (maximum) 15 yards, as in the NCAA? That's a question for the Owner's to answer. But, defenders are taught to maul the receivers, and make the officials make a call. (Then, when the officials call DPI, they get mad and question the judgment and integrity of the officials. What are ya gonna do?) Changing to a 15 yard penalty will only exacerbate the problem, since they know it will only cost them 15 yards, and not 30, 40, 50 yards.
