Seeing that oepning the website on Firefox prompts a message for me to try opening the website on Friebfox, I'd say odd is a good adjecive for this experience. It won't be odd if I was opening it on Safari or if this version of Firefox was causing issues with multiple websites (so far, I only had an issue with this one and, yes, I did try other websites that use WebGL).
Oddly, I get this when attempting to load this website on Firefox (macOS)