I’ll give you an example, I bought at BTC $36k last month and just withdrew it from exchange after all the fiat cleared in from the legacy banking channel today. It hit the chain when BTC was $42k, so these jokers would think the cost was 42. You can’t get an accurate picture from on chain data alone.

A better analogy would be like looking at clearing house data, and examining the net number of shares bought or sold at each broker, to determine how many individual investors are in the red. Even though the price changed throughout the day and you're only looking at the price at settlement time. And the net doesn't tell you anything about how many investors actually traded.