Zanshin is more evident to an onlooker when one is throwing only one person and can follow through, or maintain projection of intent, in a more exaggerated way than one could if one was dealing with several attackers. I think what many would point to in a person's technique as an indication of zanshin disappears from view when one must sort out attacker's in rapid succession. This doesn't mean zanshin is absent, only imperceptible to outside observation. I'd be careful, then, not to reduce zanshin to something in a technique that can always be seen. For myself, zanshin has more to do with feel and intent than something specifically mechanical.
In the old Asahi News film of Osensei, especially during standing techniques, he frequently adopts postures at the end of throws that I suspect are, at least in part, to demonstrate zanshin.
https://www.youtube.com/watch?v=98yRuBkUBGQ