Unfortunately there is no way to hook in and alter the results of the Copy Selected as Table method. If it is possible to show an "Export Friendly" view that is not categorized, that is one way to solve the problem.
I'm not sure how useful it will be to you, but many years ago I wrote a sample project for exporting views to Excel, and that should handle categorized views properly. There are surely other options available by now too (though I'm not familiar with them).