Oddly enough, 15 years ago an electrician I was working under told me just the same thing, except about junction boxes in 1-ph 2w circuits - it's usually the neutral that burns. I can't say much about that since thankfully I haven't encountered too many loose connections. This was in Europe (Schuko territory, i.e. no polarisation) so left vs. right hand couldn't be an issue. Besides, junction boxes use loose connectors, so no correlation either.
