Were we not talking about plug in charger and not sockets with USB power supplies built into the sockets.
The discussion was originally about how many multi-way extensions could be plugged into a ring circuit. It then moved on to the possibility of plugging in 1000 USB chargers, into those multi-way extensions and the possibility that if all were suddenly powered up at the same instant, it would likely take out the 13amp fuse in the multi-way, possibly even the 32amp MCB, maybe the cut-out fuse too.