With apologies for not picking up this topic sooner, I'm not personally aware of any proposed changes to the sign in display.
With the Email address, password box and Sign in button all showing, the height of the sign in box is under 600 pixels. I'm wondering if your browser is either displaying a reduced window or more likely that the zoom is set to more than 100%. For example, if the browser was set to 125% zoom then you would need to scroll down to see the full sign in box.
On a mobile browser it's easy to just swipe up to keep the active part of the sign in box on display.
