That doesn't sound right. Even 95% of max heart rate is sustainable for a long, long time. Intervals one can only sustain for 30s are way above VO2max intensity deep in the anaerobic zone. Heart rate pretty much maxes out on those.
Something like 90% approaches what you're talking about, maybe being sustainable for 15 minutes or so, but that 5% makes an enormous difference.
From what I can tell 220-age seems to be a rough population calculation - sort of like BMI.
It is a starting point, but fit individuals increase their max heart rate and should take a stress test.