Well, The WiFi Adapters Have Limits, For Laptop It's Higher If It Has A New Wifi Chip (Because Old Ones Max Is 100Mbit/s), For Phones Limit Is Lower, Because So The Integrated WiFi Chip Doesn't Overload...
And Have You Tried Only With Phone, Does The Download Speed Increase? if Thats The Case, Then Wifi Adapter Gives Downlaod Speed More To The Wifi Chip, Who Has Higher Frequency....