[SAump]

That is not obstruction.
Ruling F2 dropped the ball and R3 most likely would have scored absent collision.
R3 may have gained an advantage by colliding with F2 first, then stepping on the plate.
IOW, DC advocating the collision prevented F2 from picking up the ball and tagging R3.
DC's point moot after PU's safe call.

"DC coach calls time, wants runner ruled out for "not sliding" at home."
Movement underway to eliminate trainwrecks from occurring in FED play.
This FED emphasis to avoid collisions adds "confusion" to this type of play.
It would appear the umpire did have a handle on the play, safe or out.