My general feeling is that line of argument feels a bit hollow; I have learned to be suspicious of any argument about our portfolios & investing that relies on how things “ought to be” without providing historical market data that supports the claim. I’ve learned that our intuitions of how things ought to work in the financial markets often lead us astray.
Instead of relying on words, we should rely on metrics. I’m not suggesting the metrics in my posts are final & definitive by any means but it is hard to see much evidence of the dynamic that longinvest claims would manifest. Indeed, it is hard to know what we should even be looking for. What is “bad portfolio management” and how does it show up? How can we test the claim?