In Yamashina, Kyoto, we practised a variation without pinning the arm to the floor but resting it on one's own thigh in a half-kneeling stance, bending and twisting uke's hand, and pushing their arm forward by one's whole body while the free hand was exerting pressure on the shoulder. Let me tell you this was a quick way to force uke into submission, otherwise the shoulder joint would have been dislocated. You sound like you may have practised a similar technique, except that you were pinning the elbow to the floor rather than the shoulder.
Be careful about thinking of that type of pin - any pin in Aikido really - as a submission pin. The thing that is IMO the original technique is only meant to provide nage with a moment during which he or she can deploy a weapon to finish uke.
Play around with someone who trains Systema frequently and you will be aghast at how pins that only hold one arm down can be escaped from. Submission requires control of more of the body.