Seeing as I never claimed that in the first place, no, I'm not providing math for it. Here's my actual claim:
1) The DPR model used for analysis is imperfect, and one of the imperfections is the way it doesn't take damage overflow into account.
That's not even slightly the same claim as:
2) The 5e designers deliberately reduced TWF to make it comparable to other options because of the way other options were weaker than they appear given the simple DPR model.
That second claim is a reasonable paraphrase of what you are saying I'm saying,
Again, I never claimed that TWF was up to par with other martial options. I claimed that the DPR model was simplified, put forth an edge case where it demonstrably breaks down, and then used that to indicate the difference between the argument that TWF gave options and the argument that just hitting for less damage gave options.