Very different wifi speeds from iMac and iPhone in same location

I re positioned my Xfinity gateway from next to my iMac to a more central location to mimprove coverage and after doing so I checked the download speeds on both my iMac and iPhone 12 and noticed that the speed was approx 200 mbps on the iphone but only 28 mbps on the iMac.

Next to the gateway I am 500+ mbps so there is plenty of speed to be had.

Does anyone have an explanation as to why such a difference?