Only two commenters suggested this approach - I suggested it back in 2015 and again in 2022 (the background to this page is part of the 2022 letter), the other commenter (the friend and colleague I mentioned above) "borrowed" heavily from my comment letters (see footnote 208 on the bottom of page 56 of the final rules). So I accept full credit or blame, depending on how you look at it.
Actually, as I mentioned above, it wasn't really just my idea, it was proposed by the SEC in 2015 and was consistent with much of what I was thinking: look at changes in paper gains over each year (like annual change in assets on a balance sheet or someone's checking account balance). The SEC's 2015 proposing release had this approach hidden in the Economic Analysis section - I'm guessing that not too many people actually read this section.