@TandS 

I've noticed the same thing, but I chalked it up to being the average latency of all connections...not just one to your ISP or nearest Ookla site.  Will be interesting to see what comes back from TPLINK here.  To be honest, real world average latency is a more useful stat.  Why you ask?  Well one of my ISPs, using FTTH promised 'Up to 500M' symmetrical for their 'Fibe' service.... but there's only one way to get that.... and that's via their own speedtest node, clearly deep inside their network...because if I go to a speedtest site from Ookla or any other publicly available one...my throughput drops to 50-60% of the 'captive' node.  So clearly the bottleneck (throttling? cough cough) is in their internet peering routers/firewalls.