Really it’s just being smart. In Goodell’s NFL with the player conduct policy no matter what the charges are he’ll be suspended for a good long time (at least half a season, probably indefinitely) so might as well get him off the roster. Plus it helps separate them during the trial, so hopefully the press won’t be asking for player and coach reactions every day.
The Cowboys didn’t do it with that killer Josh Brent. I think he’s still technically on their roster.