Derek Lyons wrote:

NASA is now stating in an article on Spaceflightnow that a) no
recontact occurred, and b) the spin was not entirely unexpected due to
the CG of the USS being well aft.

To be pedantic, NASA says that they did not see recontact. They don't
state there was no recontact.

When I watched the video, the feeling I got is that the first stage
started to flip during a period where second stage had been unlatched
but still being accelerated by first stage. And when first stage started
to flip, it induced that movement only to the base of the second stage
which then started to separate and flip as well.



But I am puzzled:

##
The booster's roll control system also functioned perfectly, spinning
the rocket 90 degrees a few seconds after liftoff and keeping the
vehicle stable throughout the flight.
#

I can understand the shuttle needing to change it orientation so the
wings and control surfaces are in the right orientation.

But for a symetrically round rocket, why would it need to rotate 90° ?
What does that achieve ? Why not place it in the right orientation on
the pad to begin with if it needs to be in a specific roll orientation ?