I believe this is a rendering optimization leaking through to UX. It's a bit of a pattern in recent MS UI, especially their "productivity" web apps. Another exa

I believe this is a rendering optimization leaking through to UX. It's a bit of a pattern in recent MS UI, especially their "productivity" web apps. Another example I saw a couple years ago: Ctrl-A in Outlook Web Access only selects the visible messages + a small number above and below the visible messages, because the selection logic only has access to the currently-rendered items. That's my guess, anyway. I've implemented controls with this so-called "virtualized rendering" technique and it was a nightmare to retrofit to existing controls.