I think you would be surprised.I mean, no one really races with 30-year-old rags, right?
Whilst I realise that not many people are as fortunate as I am to have a 30 year old "as new" coloured sail to unleash on the world at some point, a quick check of the photos of my club, where the Laser races in a handicap fleet, about a third of the boats use original genuine sails on mid 80s Lasers or older and none have buttons. Only one seems to have upgraded to the new Mark 2 full rig and only one non class sail. I think this is probably fairly typical of many clubs around the country (UK) where we just go out for fun and the joy of being on the water, and I don't think the class should potentially alienate these people by loose wording in the rules, which is unnecessary.
I am a firm believer in the original ethos of the Laser which is its strict one designness (is that a word?) and perhaps naively think that you ought to be able to find, boxed up in a barn somewhere, an unused Laser from,say 1972, stick it on your car and turn up to a National championship and sail with it (after adding a mast retaining line of course!).