Should I explain how I identified a relevant supervisor in my SOP?
I don't know if adding this information is a good idea, but I think your current text is not.
In the draft, as it stands, you are just pointing out highlights, that proofs that you have skimmed through two papers. You are not showing any hard work because you don't even need to understand the papers to say that the method is interesting and to quote limitations they themselves described. I am not saying you haven't worked hard, or that you don't understand the paper, but just that it doesn't show all that. So, it risks backfiring at you because it sounds sort of pretentious.

If you want to show deep understanding, you would need to "cook" some new knowledge, like relating several papers, or relating their work to other people's. Mind that it will be read by people not familiar with the paper, and they may not know what is your own work, and what is just regurgitating.

One tip I can give you is to try to give it a focus from some other field you are an expert in. For example, sketch out how you would like to introduce a different mathematical modelling technique (like, instead of solving a single differential equation, you model your system as a network of interacting differential equations, where the topology comes from blablabla). This will give them a reason to hire you specifically: you are not just another mini Prof. X, but someone that would be bringing in new knowledge to the group.

Just make sure you run this through your local expert, to make sure you aren't saying anything silly, or that has actually been done before.

If after doing this you believe you are adding new useful information that would make you look better in the face of the admission committee, include it; otherwise, don't.