I get calls for inspections all the time on wood floor repairs someone did, often after water damage. Typically what's happened is they added new flooring to replace the damaged wood flooring but now it doesn't match the existing wood floor. Many times they'll tear the flooring out and leave a straight line where you can clearly see the old flooring butting up against the new flooring. Even if it isn't a straight line, sometimes the repair is just obvious due to the color of the new flooring, like this one by a vent:
A good way to prevent that objection is to tear out rows of the existing flooring that isn't damaged and then mix the new and the old boards together:
In the floor you see above, we tore that floor back 18 inches from where the repair was and saved the material, then re-installed and and blended it together with the new flooring. That existing floor is old "caramel" maple that has darker red tones to it. We could get new flooring that we thought matched the color, but the older flooring had a tighter grain to it that you just don't find today. When we sanded the floor, though, the repair was undetectable.
Doing repairs like this is time-consuming, but in all the years I've been doing it, I've never had a complaint that the repair didn't match the old flooring.