In Seidokan ushiro attacks are from behind. The attack came from behind and you never saw it coming.
When uke is grabbing one hand in kosa dori and moving around behind nage for the other hand, choke, etc. we call it katate kosa dori ushiro mawari...
We also have at least one technique(s) where the ushiro designation is given to nage's response. It's usually done from munetsuki but could be done from a variety of attacks. It's called munetsuki ushiro kata hikiotoshi (mid section punch, behind, shoulder, pulling drop). It's very similar to the Shodokan technique called ushiro ate which can be seen
here...just not quite so thuggishly done
Bronson