Today's email blast from online music empire Reverb features a video and article about what they call upside-down guitarists, that is left-handed players who play lefty, but with the strings reversed (the low string is on the bottom). The vast majority of these players seem to have learned this way simply because they picked up right-handed models, flipped them over into the more comfortable/natural left-handed position, and never changed the string order. It looks like a lot of people featured were self-taught and didn't know any better, although some, including host Malina Moye, knew but preferred it upside-down:
https://reverb.com/news/a-brief-history-of-upside-down-guitarists-with-malina-moye
No bassists, but I have seen photos of lefties who do the same thing.