Library zoom view shows low resolution

Here's a weird bug I've never noticed before.  In loop zoom view at >100%, the image is pixelated.  In attached below, Lightroom's 400% view is in the background and MacOS preview of the .tif file is in the foreground bottom right.  If I switch to the Develop module it looks fine.  

The image is 1060 x 668 tif file, "300 pixels per inch".  

Lightroom classic 10.0 build 202010011851