I agree that reproducing someone else's experiment won't help you get your PhD closer to completion (because you should be doing your own experiments and publishing no matter what, if you expect to land that lecturing position, i.e. publish or perish).

Reproducibility is one of the main principles of the scientific method (those papers shouldn't even been accepted if they don't contain enough information about how to reproduce the experiments they describe)

If an experiment is so complex that it can be compared to redoing someone else's thesis it can be either that the thesis is very simple or the experiment is so complex that it probably proves nothing.