They are baking success into the operation by limiting the number of players they give 5* to. Given that they are projecting 5* players as being first-round picks, having only 61% of them get drafted at all seems like pretty poor performance to me.

Recruiting service: "I guarantee this kid is a first-round player."
3-4 years later, kid is drafted in the 5th round
Recruiting service: "I was right! I am awesome!"

The one mitigating factor is injury. I would be much more interested in a number that takes out those who had major injuries in college. If that pushes the number up above 80% of mostly healthy players who get drafted, I would be impressed.

I have never seen an analysis of whether stars matter that isn't statistically biased in favor of saying they do. They almost certainly do matter, but their impact is overestimated due to the design of the analyses.