I know several persons of interest who've said similar things or suggested other instruments than ES for (day) trading. Another guy I've spoken to personally never was able to make ES work for him, but is making a fortune trading fixed income futures with size.
Fixed income, and I would add currency futures too, are "easier" to trade than the ES, in my experience. The biggest problem with the ES, especially now, is likely that it can now back and fill 10 to 15 points rather than the 6 to 8 ticks we used to see pre-covid.
And I wouldn't deny that there may be various factors that would generate tradable edges but not easily or readily discernible in a price chart.
I think too many retail traders read Flash Boys and think that the market is rigged and they need to find some secret sauce, some "small crack of inefficiency" that they can exploit.
It always amazes me that want to be traders do not understand that if you want to find small cracks of inefficiency you have to look at instruments, time, and strategies that do not attract much attention.
Looking at his post, it is possible that he simply didn't write it clearly enough for me to understand his full meaning. But his "It always amazes me" and then the "would be traders do not understand" and the "small cracks of inefficiency," and especially that last phrase. Whenever I read anyone saying anything like that I get tingling behind my upper bullshit detector.
So, if he'd care to present us with an example of such a "small crack of inefficiency" I'm all ears.
But it won't be coming. And such people have a built in "No way am I going to give away my edge" response.