There is no reason our hearts can't do 250 or 300 bpm if our brain told it to. As it happens it only beats fast enough to provide oxygen and cooling as needed. As you become fitter it is not unthinkable that your muscles are working harder and require more oxygen and cooling.
I have noticed that when I started cycling seriously at 35yr, 170 bpm felt like I was going to collapse, while now 175 feels intense but doable and I max out at 182.

Also it is not adviced to base HR zones on Max HR, better to use LTHR.