I never asked for hypotheticals, I asked for actual real rules that affects a QB's completion percentage. The problem with your oh gee they didn't call pass interference like they do today would work except that there were QB's that had good completion percentages.back then. As far as actual pass interference calls back whenever and today, that is called pretty much the same. The real difference is the contact after the 5 years. Your oh they wouldn't call pass interference back whenever like they do now except the refs still miss those calls today. Just ask the saints about that. Yes it now can be challenged but if, and it has happened a number of times, if there is interference on both they just let the play go as called or not called. But you can keep reaching for whatever but it's not going to change anything. Completion percentage was/is the mark for accuracy.
.