It is for every pro if you take avg power output of average pro rider and look when the winning efforts are done you need be able to push the power after a lot of kJ. ISM underlined this ability when discussing Tadej (ok maybe bad example as we talk about GT rider but proves the point) that probably many cyclist can match his numbers when fresh, but his real ability is to push them when tired.
And there is 20 min session when tired as it checks exactly this - how your numbers change after certain kJ. It is also build into the WKO and many couches do this as part of the training (not every session of course). It is also great mental excercise.