This is always situational depending on the level of play.
The times I have seen this, I actually "warned" the runner and her coach, rather than the defense.

IMO, defense can commit OBS all day long, not my problem; but the offense has zero right to physically move the defender out of the way.

In extremely low-level rec, I have, on occasion, casually mentioned to the defensive coach that there is a an increased risk of collision/injury for those players who always have their foot on the base, when there is no throw coming in.

Lamar at UNLV 36:10
2.12.16 Lamar @ UNLV Softball on Livestream

Thanks for the link... got caught up watching this game... at 48:35 U1 rings up runner at 1B for a LBR violation; I can't see how he gets that from her actions (thought maybe she left early, but it wasn't a DDB)

After the call, all 3 umps, not just 2 ????

I saw a 2-way flinch, couldn't tell if she moved her feet.

Ok, so far no one had cited that NCAA handles this OP situation differently than the other rules.

Obstruction by a fielder that relates a runner rounding (the issue here) or returning to a base results in a player-specific warning, which the calling umpire must notify the plate umpire, who records the warning, and the PU must then officially advise the head coach. That's what happened here, and U1 stayed to address the coach with the exact observed details; U3 simply moved to where he had their blind-side back during that notification.

For those not up to date on NCAA, any repeat offense by the warned player adds a forward base award to the obstructed runner. For that reason, it has to have a process.

Fun game to watch Cecil... a little later, runner overslides 3B on a triple, gets picked off, 3B coach is ejected approx 2 seconds later...

Sorry,but I disagree with your comments on the offense doesn't have the right physically move the defense. if the first base person continues to stay on the inside edge of the base when the BR is going for more than one base on a base hit, and she gets knocked on her butt. Too bad!!! Get out of the way!!!

I think there's a pendulum swing here...

Interesting. The only rights I am aware that the baserunner has is her chosen path to a base. There is a rule that supports this.

If I see a runner intentionally knock a defender on her butt, I have another rule that I can enforce as appropriate to the action.

But you write that this is just a part of the softball game?
I am ready to be enlightened with a rule that supports this.