I'd probably agree we are overestimating the amount, but I can't explicitly state that because we'll never really have great data to work with. The only really useful data we have is the amount of Bitcoin that is in circulation. That's really the only metric that's going to be reliable.
I was one of the persons who thought for a while that we're underestimating the number of bitcoin costs as one person could render his wallet useless or wipe his HDD or have a disk/card failure even one day after he has bought his coins, especially since more and more people are venturing into crypto and the percentage of those who work with back-ups is rapidly decreasing.
But although I won't change my opinion about those new "lost" coins I also think I've too overestimated the amount of old "lost" coins and the recent events when coins mined in the first month and then the other 1000 mined in 2010 suddenly woke up makes me think a lot of those that were supposed to be satoshi coins are neither his nor lost.
One thing I was always wondering but I couldn't find a tool on it anywhere, are there any old coins that have moved on the forked chain, BCH, and not on BTC?
Although I suppose the amount would be minimal it would shed another tiny ray of light on this neverending debate.
whales= .4 * bitcoin_in_circulation = 7,452,135
most of those addresses that you call "whales" belong to big exchanges and similar companies that are handling thousands of users bitcoins so they aren't whales themselves and they are indeed the very same "ordinary people" who your title mentions.
Indeed that is the most inaccurate number of all, just a few tagged cold wallet we know for sure are holding around 700 000 coins, then we have a lot of more that are not tagged, Gox coins, Coinbase and other custodial service and not forgetting the fact that some of those in this category might also be part of the so-called "lost" coins. But I'm always puzzled why people are always bringing up the subject of how many coins are left or owned by the "ordinary" people., what's up with this, are we entering another collectivization era where everything must be distributed equally?