I spent over an hour on the phone a couple of weeks ago with the owner of Viking Boatworks in Tampa, reportedly one of the best yards on the West coast of Florida. He told me every detail of Hatteras deck construction, why the water goes where it goes, etc. He went through every repair option, including the one your friend undertook. He didn't pooh-pooh the option at all, just said be aware that it can go wrong or be ineffective, and subsequent repair has been made much more difficult. My impression is it would be a reasonable repair for a relatively small area caught early before there's a lot of wet core and delamination.