"I did initially think closed loop but then capstans would be revolving
in opposite directions? It would be an extreme way to apply tension to a
tape. "

Do you understand mechanics at all ? It helps. Those things are turning in OPPOSITE directions and therefore that deck is NOT a true dual capstan. It has two but the other one is used to regulate tapes speed in reverse. That is all.

It does not have the the qualitative edge over a single capstan deck at all, that part of the mechanism simply facilitates the reverse function. It is not dual capstan at all. To me, and anyone who knows tape, dual capstan means they both work at the same time, and in that the deck, THEY DO NOT. It is either one or the other, depending on if it it is in the forward or reverse mode. At no time are both pinch rollers engaged. Only one at a time.

When it's running look and see, and you will see.