Not necessarily disagreeing but my first car, a Mk 2 Cortina, had been lying idle for 6 years, and after checking the plugs, new battery, and a bit of fiddling about it just fired up. I certainly didn't drain the petrol, and don't even recall topping it up. It was a while later that I learnt you were supposed to use fresh petrol, for the reasons you mention. Granted a '60s Ford carburettor might not be quite assophisticated or have the fine tolerances of a motorcycle carb, but still ...
Petrol isn't the same now as it was back in those days.