First of all, the number of confirmed lost bitcoin is far lower than the amount we are estimating as lost. So, you don't know whether people are not touching their bitcoin for long time or they have lost the access.
And the result can not be correct because you don't know which coins belong to which person/institution exactly unless they publicly announced it.
Most likely they have lost access to their BTC because if they were holding it up to this point, you can see some of them have already sold some of their BTC in the market. As of today, their BTC is not moving and it has not been a move for the last 5 to 10 years. consider it to be lost or the owner might already pass away. What about those BTC that has moved suddenly after so many years from sleeping? This is what I'm talking about when I said if they still have access to their BTC, they could have sold a chunk of it to the market.