grodeni
Concerning VLC, their FAQ [1] does not mention the EU aspect: they say that they cannot pay for the license because the software is free and that "the end-user becomes responsible for complying with the licensing and royalty requirements" (whether this would be defensible in court is debatable)
[1] https://wiki.videolan.org/Frequently_Asked_Questions/#What_a...
Sure if you repeat endlessly a task which is not related to the objective, it may fail to prove successful (without much surprise). However, if I repetitively compare images of one correct coin and one incorrect coin, I am pretty sure that I would improve in some way, without putting so much effort in the process. If every day someone recalls me the position of the nearest fire extinguisher, I will certainly learn this information at some point, once again without much effort.
And this type of wrong arguments can be reversed against the author thesis. Try to learn a new programming language while doing a one armed handstand, the difficulty will be way higher, however I doubt that it will generally improve your learning pace. Does that mean that difficulty is not a key to remembering? Nope, only that it is not per se a sufficient condition to remembering.