i have a few campagnolo triple sets (no Athena), none had these through-holes, but i've seen pictures of after-market modifications of various crankset types that did.
This is what a factory triple of roughly that era looked like:
its a Veloce not an Athena but there was a lot of trickling-down through the group hierarchy in these years - making dies for Aluminum forging is expensive.
My Victory/Triomphe triple *does* have spacers for the third chainring, but these sit on cast sockets on the crank.
bottom line, my money is on aftermarket/homemeade