These threads really do bring out the idiots that make outsiders hate ‘historians’ and classic posters. Embarrassing to read, even as an admirer of the old timers.
I have a degree of sympathy with this argument, but let's not get carried away with it. If the fighters of the 30s had to deal with southpaws at the highest level, then they would obviously have adapted to it. Some would always have adapted brilliantly to fighting southpaws, and others would have been like a robot malfunctioning. Also, while southpaws were generally drowned at birth back then, you did still come up against one from time to time.
If they had to deal with them, sure. But it would have taken a period of acclimatisation, and like you said there's no guarantee who'd adapt and who'd have problems. Dropping Lebedev as he is into the 30s environment as it is and I think he makes some major waves. It's simply unrealistic to expect every top fighter to adapt on the fly to him.