Well, you claim that, but that's not what basic economic and monetary theory would predict (as we've seen in fact happen) about suddenly halving the supply, inflation rate, even in the book "The Bitcoin Standard" itself.
Regardless of how the mining scarcity is implemented, that really won't do much right now when talking about the volatility. Bitcoin is volatile simply because it's being widely used as a speculative investment, and not really as a store of value. A good percentage of all the bitcoin holders bought bitcoin for the sole reason of making profit, and nothing else; hence we have these huge hype cycles. Bitcoin could already be at 21-million mined BTC right now and bitcoin would still be very volatile.
I think your "solution" to reduce price volatility and increase price would only work if we assume that everyone simply just holds; which is definitely not the case.
Bitcoin's 4-year [edit: block-reward] halving schedule arguably exacerbates wild price fluctuations, instead of a steady rise.
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