This is bullshit control, here are the facts: -
Tony Gilroy (brother of John Gilroy, who was one of Edward's editor on the production) was hired on during the reshoots to help write some of the new material (hence the screenplay credit) and to serve as a *second unit director* alongside Edwards.
The nature of the reshoots being mostly character based and involved altering bits of dialogue within existing scenes, as well as a few embellishments like the brief introductions to Kassian, Jyn and I think the Vader scenes were re-contextualised.
Gareth Edwards was never fired off of Rogue One. At all.
Pro-tip: Director's who get fired absolutely do *not* stick around to do press for the movie, are not asked to record commentary tracks for the BluRay, do not show up to Star Wars Celebration to participate in panels and most of all, do not
stand around for an hour dressed as a Stormtrooper to prank someone else's panel.
This was not a case of a Director that went off the rails, this was a Director who was a good team player and recognised that this was Lucasfilm's toybox and he wasn't there as an auteur director. The film needed help to get it over the final hurdles, so help it got.