This kind of threshold work sounds like Trevor’s 5x5s at threshold with an HR limit.
I listen to Magness’ podcast regularly and they have been talking a lot about flux traning, float training, Igloi intervals, Marius Bakken, ingebrigtsen training, etc.
All of those methods are broken interval training.
It’s left me wondering why these kinds of intervals aren’t seen in cycling. They aren’t like Billat intervals which are all out and then with an easy rest period. One idea I came across is that hard running is very hard on the body so breaking it up allows them to do a higher volume. Cycling isn’t very hard on the body so we can do longer, continuous intervals.