Walmart.com didn't work for me on FF for about a week, and it did work on edge and chrome (still broken on FF when I disabled all my add ons). However, they fixed it and it works now. I think it was just a problem with the build of the website, and wasn't intentional because it definitely works now.

I think that's what's more likely - temp problems that could affect any browser until their web dev fixes it. Not anything malicious like intentionally blocking a browser.

And then, it's just Walmart. It's nothing that really mattered.