"But again, you may be getting lost in the definition of what exactly is "high intensity", when the term gets conflated with "Lactate Threshold" training, because historically in the United States, Lactate Threshold training is around the classic 4mmol point, which is typically around 91-92% HRmax. However, these guys are doing base 'Lactate Threshold repetitions' well below that intensity, if they are keeping their Lactate below 3mmol!
This is a major point of confusion on this topic, evidence by the many questions regarding how they can do multiple lactate threshold reps and sessions per day, and on successive days! The answer is because the intensity of those reps is lower than what is generally assumed to be Lactate Threshold Pace!"
It IS not high intensity training. It is long term aerobic training. The treshold repetitions (fore example 12X 1000m) are run at lactate number 3.1-3.2, With 2 sessions per day 3 days in the week.
But they are ALWAYS having 1 day with recovery runs in between.
And yes it is a little confusing that it is call TRESHOLD training since they are running well under the treshold (to anaerobic exercise).
Their only anaerobic training in the base training period is the hill sprints.