I've been dyno testing motors since 1990.
I have done the rocker swap waaaaayy too many times to remember....... And in the last 10-12 years it's usually at the customers request, in an attempt to unlock some magic.
I don't know what people "think" they're going to find, but from what I've seen, particularly when it comes to bb mopars with std architecture heads, as long as the valve is open far enough at peak piston velocity so that there isn't a big pressure drop across the intake valve at that point, then getting the valve open even faster and farther will yield little to no gain.
There are some general exceptions to this, but that's usually how it plays out on the running motor.
On one occasion..... On a combination that was pretty air flow limited...... Where I was as sure as I could be that going from a 1.5 to 1.6 on the intake rocker was going to show a nice improvement....... I was wrong by 180deg.
The motor lost 15hp by adding the 1.6's.
Messed around with lash, jetting, timing...... All to no avail.
Put the 1.5's back on....... Power came right back.

That's the most extreme example of the rockers really not helping, but I have seen the higher ratio make less power on a number of occasions.

As it is with just about every other aspect of engine building, there are very few things that "always" make more power, on every combination.