Comment by Acconut

No, I do not think this should be implemented. The proper way (in addition to server-side validation, of course) is to utilize JavaScript in order to verify the file's size. This solution also allows different maximum sizes for different file types as one example in the discussion shows. Using JavaScript also adds additional flexibility when trying to achieve custom error messages. In general, I think the HTML specification is getting quite bloated these days, but this is not the place to discuss this.