Jason I think you are right
I actually measured a mk1 xr2 and mk2 xr2 short shaft including cv's this week .
Mk1 xr2 was 46.5cm
without the stub that goes in the gearbox as its still keeping oil in the box !, that's from the very end of the threaded bit the hub nut screws onto till the centre of the shaft inside the gearbox side of the cv giving
57cm total length .However the mk1 cv can move in a lot to shorten the total length and as the gearbox stubshaft wasn't fitted I haven't an accurate measurement yet.
Mk2xr2 with box cv's fitted (that's what it was sold to me as) total length end to end was
58cm which is hardly any different to mk1 , I always thought there was an inch difference but the mk2 xr2 cv cannot be made much if any shorter as the cv's won't compress in like a mk1.