They use either an ABR-1 or a Nashville on everything, so I agree, the spacing at the bridge itself is always more like 52mm. They do notch the saddles by hand and sometimes they're centred, sometimes they deliberately seem to go a bit wider.
I haven't had my hands on many real vintage Gibsons, maybe the saddles were spaced a little narrower in those days? Or maybe the strings always sat towards the outer edges of the bridge-pickup polepieces. :?