"Implausibly, BT also claimed to have boosted download speeds from 6Mbps to 100Mbps+ on average during testing."
It's fairly, but not entirely, implausible. I just put a mesh network (for that is all that this is) in my house, and 1) it reaches every room of my house now (as I put the disc-shaped objects in good places) and 2) I get massively improved speeds. For example, in my study, far away from my original router, I now get 109.3 Mbps using the network, as tested two minutes ago. Note that disc 1 of the mesh network is plugged directly into the router via cat6, so the (Virgin Media) WiFi is not used at any point.