Well hidden and well spotted.As it says on the tin.
Gelcoat retouch paint
Often there are scratches that are difficult to fill with gelcoat filler . I might give it a go.I think I may have seen some touching up done with this - it would explain the problems re-repairing with actual gelcoat. It appeared as a much thicker, more opaque layer than normal spray paint. Not bad for a bodge, no good for a repair.