“but doing so at <50% of VO2 max or your lactate threshold, i.e. less than 50% of the max power you could maintain for 45-60 minutes“
This implies that threshold and vo2max are synonymous—this is not true, as vo2max is roughly 106-120% of threshold.
The bulk of one’s training should be Zone 2, which is roughly 56-75% of threshold (if using the Coggan zone methodology)