That would've been impressive for sure! A somewhat recent world record[1] I just found shows a blindfolded simul for 48 boards, with 80% win! (All boards correctly turned, I'd expect and hope!)
The games in the article must've been a normal "simul"[2], which was what I enjoyed playing too.
Moves are played by square names, and with the board turned around, the king and queen are on the wrong squares (not to mention all other pieces, at least given their color). I imagine it would be an utter nightmare, but have no experience with it myself.
Well yes but the squares are the same. The king starts on E1 by definition, even if the board is turned around so that the markings would indicate it starts on D8. It might be confusing to the person reading out the move to the blindfolded player, but the blindfolded player would not have to deal with anything out of the ordinary.
Yes, the person would have to both call out and take in corrected squares, or else put the onus on Kasparov (which is what I was somehow imagining they did...).
The games in the article must've been a normal "simul"[2], which was what I enjoyed playing too.
[1]: https://www.guinnessworldrecords.com/world-records/72345-mos... [2]: https://en.wikipedia.org/wiki/Simultaneous_exhibition