Because i am assuming that waystones either work or they don´t.
Boney says a lot of things. If you look hard enough, you will find things that contradict themselves. That is why whats in the updates is the highest form of canon.
We know there is a Nexus, we know Praag is improving infinitesimaly slowly. That is enough for me to think there is something rather specific about the local network, and that adding onto it either won´t meet with Ice Witch approval or won´t directly work well. Neither of that contradicts anything that Boney said, it just builds hypotheses on back of what we do, in fact, know of the current situation and lore as presented in quest proper.