I've been doing the CTS program for awhile now. The way the program is set up, steady states are done at or below LT (8/10ths perceived effort).
The program also has TT intervals which are 9/10ths perceived effort.
So 2x20 efforts in the CTS program can be done just below LT (Steady states) or as hard as you can hold for the time (TT intervals)
Both have their place. There's pretty good data that doing the steady states gets you most of the advantage that doing them balls out gives you at a lower cost.
And then the TT intervals are done in the final prep phase, to really push you.