I've been running triples for 45 years. Many had rub. Some of them I set up intentionally so they rubbed. (Before ChainWatchers, that stopped a lot of deraillments.)
I'm still wondering what is the crisis that rub causes. Is it leading folks with sensitive ears to deafness? Insanity? Are there laws against rub I don't know about? Yeah, it does wear out FD cages but on quality FDs with substantial cages, that takes quite a while. And that wear is very easy to check. Are front derailleurs an endangered species? (That might be it! With 1X, we need to protect every living one.)
I guess I will have to keep studying this issue unless someone here can help me.
Ben