Many years ago, I would run across the “Hyd cam won’t rev” scenario pretty often.
And on a few occasions I actually did some spring testing/swapping.
Keep in mind, the first spring combo was presumed to be adequate for the task at hand.

Each time I went thru the trouble of increasing the spring loads, I was rewarded with essentially zero gain in rpm.

We chased it around pretty intently on my friends Pontiac Stocker.
The one test we did that was worth nearly 1000 additional rpm was running solid lifters, lashed at .004, on the Hyd cam.
Of course, that wasn’t legal.
This was before the Schubek lifter days.

On more than one occasion, the added spring pressure resulted in the power nosedive from lifter unhappiness being even more of a light switch affair.

I wasn’t really sure what the actual problem was then, but I understand it now.
It’s lifter collapse………and more spring doesn’t solve that.

There was a dyno test in MM where they went thru that lifter collapse situation.
It was after we had already been thru it with the Pontiac.

Search “mild mannered mauler” from like 2005.

The main thing I was interested in seeing on the 505 I referenced above was whether or not the combination of cam lobes designed for prolonged higher rpm use, combined with the pretty new at the time Comp Evolution lifters, would allow for issue free valvetrain operation solidly past 6000rpm.
On that engine at least, in my mind……… it was a complete success.

With 1.6 HS rockers, and springs that were set up at 150/400, there were no signs of unhappiness thru 6300.
In hindsight…….I should have attempted 6500.