Hi there, @tim.dickinson… as you know, this topic comes up from time to time (there was one just a few days ago), and I don’t think there is a better answer than using privacy rules effectively and hiding the content on a page so it doesn’t briefly flash before the user is redirected. That being said, I wouldn’t want to put conditions on every single displayable element either, and I have seen a number of folks suggest putting a group or a shape over the entire page in order to obscure everything on the page in one shot until the security check is done.
Sorry there isn’t a better answer here, but at the very least, you don’t have to modify every element on a page, and maybe that’s something.
Best…
Mike