I purchased a new house. The builder put a product on the floor that has left it
Grey and splotchy. They have tried removing it with denatured alcohol with little success and too time intensive. He wants to 'screen' and refinish the floor. Is thus possible on this hand scraped wood and if so what problems are likely to occur? Are there other solutions than reaching which is my choice.

It will be hard to screen because its not flat. All the depressions from the scraping will be missed by the screening process and run the risk of poor adhesion. I would recommend using the tykote system from Basic Coatings. It' will chemically etch the finish so you get a good bond even down in the cracks and crevices.