I get the perception of the kimura being a strong mans move, but I would have to say in its pure form it really isn't at all. The reason it's thought of this way is because a lot of grapplers miss the finer points/details of the submission,from top or bottom, and then compensate for their lack of technique but using all their arm strength. The figure four grip itself is one of the strongest out there and provides an immense amount of control; on top, the one applying focus on keeping a 90 degree bend in their opponents arm, and also keeping the wrist of the captured arm glued to the mat at all times. Then, after stepping over the opponents head and switching the hips, this exposes space between the mat and their opponents back, allowing for the captured arm to be behind the defenders back for the finish. I would say the best example I've seen of this is George Sotiropolous finishing Joe Lauzon; G-Sot trained with my academy during this time period and his kimuras were different and more deadly than I've ever seen.
If done properly, the attacker uses their entire body to finish the kimura, and the entire body will always be stronger than an isolated arm.
There are other grip details too from other positions that make a world of difference. Like when being applied from bottom, it's important to do a motorcycle rev (curl) with the wrists and keep the tricep of the captured arm glued to your chest, and then turning your hips and whole body, not just using the arms to rip the isolated arm free. Also, the catchers position, which GSP used against Hughes (third fight) and Hardy requires similar grip details for greater efficiency; it's important to keep the elbow to the chest, motorcycle curl the wrists, pull the wrist of the captured arm as close to the attackers own hips as possible, and then ripping the arm free with the body but also by pulling the arm away from the defenders grip first and then behind the back. If the opponents body is a vertical center line up and down, and the kimura needs to be applied on the left side of this line, the opponents grip should be broken by first ripping away to the right side of this line, because it's pulling away from the opponents grip, and is on their weak plane; trying to take the arm behind the back immediately plays into the direction of the defenders grip (if trying to grab their own arm or hand to defend).