I'm still trying to figure what's meant by a milonguero style back ocho without pivots.
In the milonguero style of dancing, the line created by the placement of the foot is NOT perpendicular to the line of the hips. The hips remain facing the leader and the foot ends up crossing to whatever extent is necessary to land where the leader puts the follower. The video I posted of Mariana Galassi shows this in an extreme of crossing side steps, but they can also be done traveling.
But the key is that the followers hips face the leader and the leg does whatever it has to in order execute the step led. The extent of crossing depends on various factors of how (and where) the leader moves with his lead. If he travels, it will cross less. If he doesn't travel, it will cross so much as to be more of a side step than a backstep.
This video of Rebecca and Evan might help even though it is for a molinete, the same principle applies.