I wanted to read more about the article that OP copied so I did a quick search and found the article on
fortune. The estimate came from Chainalysis I don't know how they've come up with such number but if the estimate is nearly accurate that's just crazy. Lost Bitcoin can still be retrieved though who knows someone might end up generating an address with some Bitcoins inside.
My view is that I don't totally succumb to the believe in OP's hypothesis that lost bitcoin are more like the reason that bitcoin gained value. We have coins that are not close to 21m in maximum supply and are not close to the price of bitcoin too. I think the technology, use and community are responsible for that.
I agree those lost Bitcoins won't boost the price for now but in the future once the block reward goes to 0 that might be the time where the lack of supply kicks in that is if Bitcoin is still one of the top coins after a hundred years.