Threshold intervals HR in the low 170’s if I’m doing them correctly. If I throw a 20 second all-out sprint at the end of these intervals (10 mins threshold then finish the last 20 seconds all-out sprint), HR bounces up to 185, which I interpret as my max before things just fall apart. Just to say that you can be totally worked and max’d out in your breathing and effort, but then tapping the anaerobic/neuromuscular pathways leads to short bursts of even higher HR.
I also usually get close to my max HR during a proper ramp test.
The formulas for estimating max HR are based on bell curves for the general population. I haven’t seen many people doing extended periods of structured training for whom the formulas are good estimators.