Agreed, but this was more of a substitute teacher gig. The script, the set-pieces, the action sequences, effects, etc. almost assuredly stayed nearly exactly the same. From what I understand, Rogue One had legit story problems, where as Solo had more of a diverging tone issue.
Also, because Howard didn't bring on his own crew - for instance, the same cinematographer (the amazing Bradford Young) and camera team were constant across both iterations - I bet they shot many scenes exactly the same as the first go around, just with more suitable performances and dialogue here and there (and in certain instances they likely got to improve upon techniques used prior). All Howard had to do was stick to the curriculum, so to speak. His job, I imagine, was more about ensuring that the performances and tone were more in line with what Kennedy and Kasdan had originally hoped for.
In other words, Lord & Miller and Howard all likely had the same coloring book to work with, with all the same pictures and lines, but Lord & Miller started using colors that were a bit too "out there" and colored outside the lines one too many times - where as Howard, with the exact same pictures, used the intended colors, and stayed inside the lines. That's all Kennedy needed anyone to do.
Also, remember that a decent chunk of the reshoots were strictly because Michael K. Williams wasn't available again, so they had to reshoot his scenes with Paul Bettany instead.
Point is, I don't think this is near the issue Rogue One suffered. From everything I've heard, the story isn't even remotely the problem in this case. It's that, originally, Lord & Miller weren't sticking to it.
