Oil futures markets are less than perfectly elastic. At the time of the oil future expiration, a bunch of real barrels of oil change hands, so a pretty good model of the market is to just think about all trades as predicting that single big final transaction between “real” economic actors. It’s pretty clear that the price “ought to be” somewhat inelastic, because if I really need to buy oil, someone has to drill more / drain a reserve and sell it to me.
In the case of the stock market, there is no physical cost to being long/short the stock, just risk/capital costs that can be diversified away. Consequently, it’s easier to have the intuition that the price really should be quite elastic around some consensus “fundamental value”, and this intuition is reflected in much of the literature. But I think it’s a fairly bogus assumption, unless the stock is really easy to model there is no strong consensus price around which people can be elastic, and supply and demand are important.
Highly traded speculative assets that nobody knows how to price (e.g. GME, TSLA) are the least efficient products in this flow shock elasticity sense; they ought to mostly move on flows, because there’s a lack of other information to form a consensus price around. The most efficient products are arbitrage spreads.