It's still being done... By home brewers in my area unfortunately!I had always heard as well that it was soured with soured guiness as well... obviously with nothing to back it up.
AFAIK, that's an urban myth. Although possibly it was done in the past.
I had a local homebrewed Dry Stout that was lactic and Band-Aids. UGH! Upon asking, she said it was because her temperature control broke. Since that can't be the cause of lactic/phenols I probed further and then quickly wished I hadn't. Turns out she leaves out two pints of Guinness "until is sours, because that's how Guinness does it" and then dumps that in at flame out. o_O