I don't disagree one jot or tittle Neil!!
Ideally, give me neither problem - and I count myself lucky to be in that happy position with my untapped A.
The 'per-A65' ball & spring reversal is probably a very good idea . . . . but for now the original design works OK on mine, after replacement on the one occasion in over 13 years and a good few miles that the engine has been (fully) apart. Perversely, with the SRM sump plate and plug, my A is by far the easiest machine I own to drain out in a hurry - yet I never have to.
But . . . my Nortons and my AMC twins suffer badly despite best efforts, and it really can be a pain to have to drain them out after not very long left standing. Apart from anything else, the AMC alloy crankcase bungs aren't the best design ever seen in the history of motorcycles - damaged threads aren't rare sadly due to their being at an angle, and they are a bit tight to get onto with a decent socket. The Nortons' mega-sized after-market plugs (for which you need a lorry-sized set of weapons) at least have small central drain bolts to spare the crankcase threads . . . Small mercies always welcome!
A buggered engine isn't an inevitable consequence - but like all folk with oil taps, I certainly acknowledge the risk (and regularly check the pesky cut-outs on the mags, flimsy darn things which can and sometimes do go AWOL.)
So to Roger's original Q I'd say yup, it's contentious and views are entrenched, but 'On our heads be it and may we Be Very Aware!)