Thread:Talk:ResourceLoader/Migration guide for extension developers/Mixed purpose modules/reply

The problem with what you say above is that the "top" property is not available until version 1.19, which is not yet stable. So with version 1.18 doing it the way you say, the browser displays unstyled html for a second before the styling is applied, which is a very unpleasant user experience. I would rather trade a bit of efficiency for a much better overall experience.