IE 6 defaults to what is now called "quirks mode". You can add a doctype to specify "strict mode".
IE 7 should default to strict, allowing a doctype to specify quirks.
This way, anyone who is intentionally writing to IE 6 quirks mode can use a doctype to specify this. Anyone trying to write to current standards will be automatically supported.
From your snip, it looks like thie may be what they're saying. Now if your site is intentionally writing to the IE 6 quirks mode, what exactly would you have MS do in IE 7 to make your site work the way you'd like? I'm no fan of MS, but I don't see how else they could deal with this.