Hi Peter,
The sloops will certainly be closer winded than the more common ketches, but still not likely to get as close to the wind as a modern fractional rig with swept back spreaders. A cutter arrangement in the fore friangle is also likely to be less close winded than a single genoa. However, a racing rig then and now, normally entails a taller mast giving more sail area and a higher aspect ratio, both features making a yacht faster, especially in light airs.
I've never met Bob Perry but seem to recall he was the architect behind the successful Cheoy Lee cruising yachts and a quick internet check puts him at 5 years older than me. Despite my youth, I was crewing on racing yachts in the 1960's, mostly rather smaller than the Moody 44 but I did a few trips on a 46 ft. Rebel , so I remember yachts of 1970's vintage very well - it's the more modern ones that mystify me!
Peter