[CelticNHBlue]

I concur, this seems like it was a no call situation. From the description, it sounds like the defensive player made a choice to make the play in a location one step back from where they were. I don't see how the runner impacted this decision.

IMO, players have choices. On offense, a runner may choose to slide directly into a bag or make a sweep slide for the back of the bag. You only have obstruction if the defense took away one of the runners choices by impeding their way to a portion of the bag. The defense may charge the ball or let it come to them. It can only be interference if the offense took away one of the defensive players choices to make a play.