I have a racing friend who is an electrocardiologist (pacemaker surgeon) and I will ask him. However, max HR seems to be allusive and is only relevant if it can be ascertained by calculation or measurement. If I measure a higher max running than cycling which one do I use when setting zones for cycling?
However, this is more of an esoteric discussion and will not help OP. I think BikeWNC had the correct answer.