The heart rate zone stuff is just silly. Lots of overly simplistic thinking given the wide individual variation in both peak HR and active muscle metabolic qualities. But some physiologists and coaches, for whatever reason, just seem compelled go to a one size fits all. Many of the readers and posters here don't realize HRpeak can be changed in athletes' testing with merely the additional encouragement to continue the test, especially in the over 40 crowd. Astrand decades ago recognized that elite endurance athletes seem to save a gear for racing. so which HR numbers shall we go with?
Too many factors that contribute to the adaptation process and all of this perspective ignores non-steady state HR kinetics (duration, work/rest and intensity dependent), within individual heart rate variability influences, fatigue process and aspects related to fueling, depletion, dehydration, weather, fiber type, and weather. And even the same HR can mean drastically different circumstances in the active muscle, including motor unit rotation, blood flow distribution, work of breathing and so forth. (See for example, Dempsey's Is the lung built for exercise?, Wolfe memorial lecture)
Now the UK kid in the short video above is smart enough certainly except the lactate break points he describes don't always occur, does this fact matter to you? This sort of analysis also ignores the influence of testing protocol and modality, especially stage duration, impact of overreaching, blood draw site, mathematics and data points,and monthly, seasonal and circadian factors. Determination of these thresholds is unreliable.
And if nothing changes in testing aspects, performance capability can be quite different.
Anyway hope this helps.