I have noticed that the AMP Validator,
(a) doesn't tell you how big your CSS file is until it is too big. (b) when it is too big and you manually count the length of your CSS it still seems to be smaller than the 50,000 limit.
Anyone have any ides why?
PS My solution is to properly compress for the page the CSS but I can't do this easily in real time so a few edge pages get through with slightly too large CSS files (but that are still less than 50,000 when I count their lenght).