Special Dedicated Harlen Sharp Edelbrock RPM Rockers?

I was looking on the Harlan Sharp Rocker Descriptions
and it has a special Rocker that only fits RPM and Trick Flow
Big Block heads and nothing else. I have always just run a regular
roller rocker for standard Mopar big block heads with no issue.

The Geometry and fit looks fine and I have made 100s of runs with
them.

What have I overlooked and missed?