Does RT-AC88U support gigabit wireless?

I have an RT-AC88U ASUS router and recently updated my fiber internet to gigabit. This is CenturyLink gigabit. (Actually they only promise 940.)

I have been testing my new service to see if I am actually getting gigabit and indeed I am.

BUT, I can only verify this with my ThinkPad X1 Yoga (3rd) when plugged into the Ethernet port. Wireless never gets above about 400.

SO, to my question, is this low rate due to the wireless capability of my ASUS router or my Thinkpad?

P.S....

Does RT-AC88U support gigabit wireless?