I was about to say this.I'll mention in passing that there isn't really a "6-8 expectation" unless you're restricting encounters to Easy combats. Maybe 6-8 was typical before they flipped difficulties thresholds from ceilings to floors in Basic Rules 0.2, but nowadays 5-6 Medium Combats is about all you can expect to get before you hit your daily difficulty budget limit (which is still a ceiling).
E.g. at 11th level, to choose one at random, each PC would get 11,500 XP of difficulty, where Easy is 800-1599, Medium is 1600-2399, Hard is 2400-3599, and Deadly is 3600+. Three Hard encounters is all you get, or six bare-Mediums. Getting eight requires you to dip into Easies and keep the rest Medium.
It seems like people are over-emphasizing the 6-8 guideline.