Questionable legionary formation on History Channel

[Jormungand]

As a longstanding fan of HBO's Rome series, I thought I'd bring this up.

https://www.youtube.com/watch?v=Ndh3b9wC-A0

Watch from 4:25 onwards. The legionaries appear to be using a very strange formation involving the rotation of men from the front rank directly to the rear of the formation, the next man in line taking his place. I've read Goldsworthy's Complete Roman Army and don't recall any mention whatsoever of such a formation in use at the time.
It would seem highly dangerous as the legionaries fighting in the front lines would turn their backs to the enemy, leaving them exposed and wide open to attack while they retreat through the ranks.

While I don't believe for even an instant that the Romans ever used this formation, at 4:46 in the video there is a ? History Channel excerpt showing this exact formation playing out as well.

Correct me if I am wrong, but isn't this meant to be the History Channel?