You can't read from blastr type of relays. They are proxies, talking to other relays.

I write the type of data you mention to blastr relays in addition to user write relays and, for extra safety,  "bootstrap" relays like purplepages.

But I don't read this metadata from relay proxies, only from bootstrap and user write relays. 

 Good point, I didn't consider that they don't accept REQs.