Everyone is different. The max heart rate 220 minus formulae and it's variants work for most people i.e. near the middle of the bell curve, but can be incorrect by 10, 20 or even 30bpm for some people. Both high or low error.
I've done a lot of endurance stuff and when in my mid 40s my resting HR was low 40s. Not super athlete but pretty fit, finishing in top 20% in most events. Formula suggested my max would be approx 175 but I would occassionaly reach 212 and regularly saw >205. In one particular 2hr MTB race my average was 184. Around then I had an ECG for a work medical check and all good, no issues. When I was telling doctor about my health and fitness he told me I had a 'revy' (sp? revvy? revvie?) heart and be careful, to ease off if I felt unwell, weak or dizzy, but don't stop what I was doing as I obviously tolerated it well and that just how my heart was. During 12hr lap MTB races I would set watch or bike computer beep if HR got above 155. When it did I knew to back off and I'd target HR dropping to below 150 within the next couple of minutes. Average over the 12hrs would be mid to high 140s. For adventure races involving MTB, kayak, trek etc over 1 to 7days duration my average would usually be in range 100-120bpm.