Brian Florian who wrote the article is a lone voice on this "problem". In real world applications it is a non-event. Even if he was right, which I disagree with, you get many more benefits by optimizing individual speaker crossovers. My recommendation is find the right crossover setting for each speaker as per 1/2 octave above its lowest extension and enjoy the sound.
Where he has a point is to avoid settings which send the same doubled up bass with the mains and sub ie. settings which allow you to send LFE to full range front mains and the sub at the same time. All that does is create phase issues and sloppy bass. Because the DD LFE track is replicated on the LF and RF mains as per the DD standard it is always best to cross the mains at some frequency to the sub rather than run them completely full range uncrossed.
Bottom line: Florian's article doesn't jive with real world HT listening. Ignore it.
