Isn't it still a frontal interior entry?
It is an entry to the side "into" the attacking arm. When you practice this in an advanced manner you can got "through" this arm and get right behind uke. We do it mostly for irimi nage. But kaiten nage also is nice. Or just to get behind the attacker.
In our teaching what is shown in the video you posted, is develloped over time from what you see in the video I posted.