While I'm not a Patriots fan... *technically* Cortana is correct. The two statements are just not as interrelated as we are inferring them to be.
1) Cortana picks the Patriots to win (in part because?)
2) The New England Patriots hold the NFL record for the longest winning streak at 21 back a few years ago.

EDIT - and of course I'm wrong. Ha! I did a Bing search for "Patriots 21" and got several articles referring to that streak. I'm guessing she got her data from those same sites. Evidently the Colts hold the record at 23.