Displacement filters causing loss of resolution?

I'm working on a website, that has images that will use displacement filters for some interactivity. As soon as I add them to my container, the images get blurry, even though I've got the filters scaled to 0.

I'm on a MacBook Pro (Retina).

Here's a CodePen of the issue:
https://codepen.io/elegantseagulls/pen/NowKgG?editors=0010

commenting out line 79 will show the higher resolution images.

Any thoughts on this? Am I missing something?