I'm getting 455.5 Mbps when I do a speed test using the Tether app and yet while uploading large video files via wifi with my MacBook Pro within clear line of site to the router only 20 feet away I'm only getting about 15 Mb/s. I've rebooted the router, I've tried enabling and disabling Smart Connect, I've prioritzed the MacBook Pro in the list of connected Clients. 

Also, in the past I've tried using a wired connection to the router and have also not achieved better speeds.

When I do a speed test on my MacBook Pro (connected by wifi), I get 457 Mbps download and just 157 Mbps upload. There are plenty of other devices on the network but most of them are HomePods or little things. None are actively uploading anything.

What is going on??