Obviously not dismissing your experience, just adding my own : I tried it recently on a big game that was installed on my SO desktop, and it worked great. Just had to activate the feature on both Steam instances, restart Steam, and then I enjoyed a superfast “download” speed, that was mainly bottlenecked by my drive speed and even sometimes by my computer’s ethernet port limit!

Don’t know about Germany, but in France, Dora teaches you English!