Repairing hardwood floors is not as simple as it may look. I've seen many General Contractors do a poor job of this. Usually, the biggest mistake is that they don't know how to identify the species of wood used. So, they mistakenly mismatch red and white oak. That is the case in this kitchen repair.
You can read more on the differences between red oak and white oak here: Red Oak
The second issue is that many do not know how to properly weave the wood. Often, they will do what I call "The Handyman Special" which is where the wood is all finished in one line rather than being woven in (the way it normally is). Then next most common issue is not weaving it far enough or randomizing it enough. In this case, the butt joints are too close together. Not only does this look stupid, but it causes more separation in the boards.
So, when it comes to doing hardwood repair and refinishing the floors, I'd recommend that call a specialist. If you live in the Westchester NY area, you can call the Flooring Girl Westchester Hardwood Floor refinishing. 914-937-2950. TheFlooringGirl.com