MaxFat is indeed the zone of max fat consumption.
Look at the figure with 4 tables from link below : on the lower right table you will see the fat and CH consumption curves for Cameron Wurf. MaxFat is the green area (in power for bike). To be compared with a Max VO2 around 490w. https://www.triathlete.com/...yclist-part-2_334218
For me MaxFat is, for bike and run (not swim) :
around 73% of FTP
around 53 % of Max VO2 power (from 48% to 58%)
from 65% to 73% of Max HR
MaxFat is the zone with maximum fat consumption, but not the ideal zone to train your muscles to use essentially fat, this one being base endurance zone.
Base endurance zone, to be used to reinforce muscle fat consumption while lowering lactate level (around 1mmol/L of lactate) and consequently limiting CH use to minimum, is a bit lower :
For me base endurance is : from 58% to 67% of Max HR
I do not use "zone 1, 2, 3" terms here because peoples use different references (several 5 zones definition, 7 zones definition, ...) and it become very confusing.