If you watch the release video embedded in the post you can hear both part of the acceptance speech from the makers of Flow where they explicitly thank Blender,

If you watch the release video embedded in the post you can hear both part of the acceptance speech from the makers of Flow where they explicitly thank Blender, and also can also see a special oscar scene, which I assume the creators of Flow made specifically for this version announcement. In general, there seems to be a close relationship with the creators and Blender, and the overall impression given is that the creators also think that Blender should receive part of the credit.