I use to ride oversize bikes for my size. And I did it quite comfortably. However I'm finding the smaller frame sizes recommended for my height and body measurements more fun to ride and actually more comfortable for longer rides.
I also find I like a more aero position more on them. My larger framed bikes I tended to set them up for a less aero position.
But of course my experience with them might not be your experience. So if the LBS is pushing that on you, then make them let you test ride it for 10 miles or so on your normal routes.
Larger frames also have longer cranks and wider bars. That may or may not be an issue too.
Last edited by Iride01; 09-10-21 at 08:50 AM.