Depending on the guitar, the screws that come with the
strap lock systems are often too big or too small for the existing non-modified holes. If the replacement screws are too small people talk about wood filler, glue, toothpicks etc which sounds like a messy drag. If the replacement screws are too big I can understand the hesitancy to drill holes in your guitar.
I tried seeing if the existing screws on my Jackson would work with the Dunlop system because I didn't want to drill, but the screw head itself was too wide to pull all the way down through the replacement Dunlop
strap button. A file and some elbow grease around the perimeter of the screw head for a few minutes and voila, the original screw can now be pulled all the way down through the required Dunlop strap button and secured back in the guitar as if nothing happened. Perfectly safe and reversible if you want to put the original strap button on later.
I've read suggestions which say to bore out the strap button instead, that's the same idea in reverse, I just didn't have the equipment laying around to do that. Worked like a charm.