This is more about payment and protecting NBBO. Very few scale institutions will interact with payment and that decreases the listed choices, but with the exception of spreads, NBBO can't be violated without taking out a resting NBBO and it just becomes cumbersome. Doing it upstairs is easy at times. Equity options done upstairs are not fungible and only SPX qualifies for OCC when done off the floor. There are other complications if a satisfaction order(s) needs to sent. Facilitation on a floor is superior, but as the article points out. It can take too long.
