Boyd, it is a good idea but there are problems with it. A wood floor responds to changes in humidity by moving. You can't see the movement, but the wood grows and shrinks. The movement is most across the grain qnd less, percentagewise, along the length. You can not stop this movement. If you try to, the wood will react by cupping. At the edges of the boards, the movement will mash either itself or anything you put in the gap. If you put in something like silicon, you will have problems with the finish not sticking when you apply it or flaking off when the silicon and poly move. If the problem areas are not where they can be readily seen, this is probably as good as anything. For highly visible and high traffic areas, I think that you will want to "steal" some flooring from another area or have some milled to match and replace the bad boards. Hate to say it but you have to remember that we are a litigeous society. If somebody trips and falls because of problems with your floor, or a kid gets splinters, you could be sued.
The reason for the flat is that it shows wear and defects a lot less than the glossy. It may also be a little less slippery.