It has become popular at least in Norway to copy the Ingebrigtsen model where they do a lot of so-called threshold training. It is done as double workout days 2 days a week (plus a third day with short hills at higher efforts). The morning workout is longer 5-6min repeats with 60s rest aiming at lactate levels of 2.5mmol and afternoon workouts doing 1ks w/60s rest or 60-90s efforts w/30s rest, but aiming at max 3.5mmol.
The paces obtained differ of course due to repeat length and lactate level.
The paces could be in a range from 20-30s pr km different from the longest/slowest to the shortest/fastest.
It is reported that Jakob is doing the 1ks at 2.40 and the 90s-60s close to 2.30 pr km, meaning he can hit somewhere btw his 3k to 10k paces.
The difference in muscle fibre activation is different. The short intervals will employ much more of the faster twitch than the long ones. Still it is thought of as "threshold". It is obviously not. The workouts have to give different adaptations based on the differences, but I guess when the lactate is under control, the impact on recovery is under control.
Comparing 2.40 1k w/60s rest with CV intervals with 60s rest shows they are very much the same. I guess this is just another wrapping of the same thing.
I have used long threshold reps with very short rest (20s) and that is also a way, but it demands the pace to be maybe more true to the 1h race pace. I have done 8,6 or 4min reps with 20s rest. If I do 60s rest, I can hit a faster pace more easily. I will try out the reps with 2.30min and 60s rest and compare the pace with 4min and 20s rest. I guess all variations have their purpose.
Some norwegian coach wrote he did not quite see the thing about short repeats on rising lactate levels (goes up and down). I guess the benefit is a good speed without accumulating too high lactate levels. Quality without too much recovery need.