Sure, but in the article/convo a distinction is made between selling to take profits and selling when there is a shift in expectations. That implies that taking profits here is a purely speculative move.
If there is no shift in expectations, then you should reduce your position as the price goes up, per Kelly, i.e. "take profits". It's a great heuristic. If you wouldn't buy something at the current price, why hold it?
taking profits is always a purely speculative move, but a good one. Taking profits doesn't mean you liquidate entirely, it just reduces risk.
E.G. I believe in crypto, but when btc went from 20k - > 50k i took all my profit except my initial investment. It was purely speculative sure, but it drastically reduced my risk without reducing too much profit potential if i still believe in the long term.
Talk about initial investment is not meaningful. Money is fungible. The only relevant question is what the current optimal percentage of bankroll to allocate is given the price and the expectation of future prices.