This is an interesting narrative. And one I have not proven myself. I have heard it is more true on asian dark net servers. But I would think the latest addition of Monero at Dream (I think?) would fly in the face of this a little. Dark net vendors are getting more savvy little by little.
Don't know about you lot but I like to keep tabs on sentiment on DNM forums in relation to crypto of choice.
I can tell you Monero is lightyears ahead in terms of mindshare on each forum I peruse.