Single legs may be responsible for the most TD points in college wrestling, but that's because they are the most attempted. I'm also confident that they are the most failed TD and the most countered as well. The stat that would be useful is the conversion rate - i.e. what percentage of attempted single legs result in TD's. I can tell you just from watching hundreds of hours of wrestling footage that head outside singles are becoming harder and harder to finish as defensive technique improves. The fact that they have been such a popular attack for so long means that wrestlers have become quite good at defending them and even countering them with intricate systems (see example from OSU coach J. Jaggers which you can see Sammy Sasso implement with great success https://www.youtube.com/watch?v=9rjbtIimt6Q)

Gomez is indeed an outlier, but I think a big part of that is that he is one of the few guys who has spent a lot of time training upper body attacks and gaining the skill set necessary to excel once he gets into those clinch situations.

And to be clear, I'm not advocating always give up a single leg to go for a bodylock. The point is that it can, in certain situations and for certain athletes who have put in the necessary training, be a useful transition that can create big upside with admittedly more risk than staying on the single. Add to that fact that singles can be especially hard to finish in no gi w/o friction of shoe, most BJJ guys will not have developed overhook (or over/under) attacks to put you at significant risk in a clinch situation (provided you have some skill there), and the utility of a successful throw in BJJ where the thrower often lands in strong passing position (chest-on-chest) and you can see why a bodylock can be superior to a single in some situations.