“It seems equivalent to saying that value of the USD decreases since cash transactions (USD exchanging hands) can happen instantly.”

The USD is a stablecoin. Its quantity is determined by the need for it. Average transaction speed increases slowly, and the rate at which new money is created in a growing economy subsumes that improvement in speed. But even if there were to be a quantum leap in transaction speed, the value of the dollar would not decline. Rather, the banking industry would need fewer dollars in reserve and would exchange its pre-acceleration reserves for Treasury securities, preserving the value of the dollar.

Bitcoin has no analogous function. If the transaction speed increases so that the volume transacted per second or minute or hour decreases, the value of the coin will decrease, too, because it cannot be exchanged for an interest-bearing instrument of its creator.

I have looked at the linked article. “Brief” is not the word I would use to describe your analysis. I will think about posting a comment there.