Just to reiterate, we're talking about the chain oiler hole in the back of the primary chaincase and not the crankcase breather.
I've always had the chain oiler blocked on both of my A65s. One still had the little 90-degree pipe on it, which I simply pinched off. The other one had a nut and bolt in place of the pipe.
I agree that chain lube is far superior to motor oil (or ATF, which I run in the primary) in keeping the chain lubed (and less messy). FWIW, the best product I've tried to date is Chainwax (and I've tried them all, PJ1, Silkolene, etc.).
'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.