Ahhhh!!! If life were so simple!!!!!

But life just isn't like that with most Euro sling swivel studs..... there is very little metal on the stud. If you tried to drill the hole to American standard size there would not be any stud left. Like a Porsche, with parts engineered to very tight tolerances to be enough to do the job and no more, the Europeans don't tend to use more metal than is necessary in their firearm studs.

Even if there was enough metal to drill a larger hole in the stud, the stud itself is narrower than an American standard QD stud, and there would be tremendous slop between the sides of the stud and the inside edges of an Uncle Mike's QD swivel.