Welcome to the new and wonderful world of the “modern” web, where you can be running a browser released 2 months ago and it’s considered OK to not support it because it’s not one of the big three.
I particularly adore the fearmongering security theatre used as an excuse for their not bothering with progressive enhancement and compatibility.
Now, I suppose to be fair I should concede that although I do label it as a “blatant lie”, it is possible that I might be wrong and this might not actually be a lie: It could just be that they’re simply incompetent at web development.