While this is all technically true. Lachlan and Sepp both are former winners of the Tour of Utah in the USA, which is shorter than the tour, but generally at a higher altitude with alpine climbs rivaling the staples of the Alps/Pyrenees in the TdF.
Lachlan was one of handful of pro/ex-pro riders to start tackling the Everesting[1] record as well, which is a clear example of his ability to ride at (and above) the "level of work involved" in a TdF mountain stage.