Had a long flight and I was bored, so I went through the list and wrote down the original recruiting star rating for each of the OL who've been invited to the NFL combine. It's not perfect, but I figured it's about a good a metric as we have in determining the top performing college OL.
I also added up the number of available stars for each of the OC, OG and OT positions according to 247. For this I used the number of available stars for the OL three positions back in 2015 when the average 2019 combine invitee would have been a college recruit. I know some of these kids started college in 2014 and some started in 2016, but I picked 2015. (This led to the anomaly of four total 5 star OL recruits in 2015 but five 5 star recruits being invited to the combine in 2009.) While all this is not precisely correct, I think the sample size enough to provide a valuable insight.
The results:
1. In 2015 there were 336 5 star, 4 star and 3 star recruits for all of the OC, OG and OT positions. Of the 336 total, there were:
4 total 5 star OC, OG and OT recruits
58 total 4 star OC, OG and OT recruits
274 total 3 star OC, OG and OT recruits
2. In 2019 the number of recruits by star ratings who were invited to the combine are:
5 former 5 star OC, OG and OT recruits were invited to the combine, or 125% of all 5 stars
16 former 4 star OC, OG and OT recruits were invited to the combine, or 28% of all 4 stars
21 former 3 star OC, OG and OT recruits were invited to the combine, or 8% of all 3 stars
3. Conclusion:
There were slightly more 3 star kids invited to the combine (21) than 4 star kids (16), and way more than 5 star kids (5).
But we know that the rankings are a measure of the probability of college success. And in this regard the star ratings are distributed as one would expect. Specifically, if a school signs a 5 star OC, OG or OT recruit there is a 125% chance that player will have performed well enough in college to be invited to the NFL. (The 125% is an anomaly due to overlapping years of a given Jr, Sr or RS-Sr players declaring. This would be altered for the 2018 and 2020 combines.) If a school signs a 4 star OC, OG or OT recruit there is a 28% chance he'll play well enough in college to be invited to the combine. And lastly a 3 star recruit would have a 8% probability he'll be invited to the combine.
When we sign a 3 star OL there certainly is a chance he will play very well, well enough to be invited to the combine. Specifically there is an 8% chance of that happening. So for every twelve 3 star OL we sign, one player should be invited to the combine. And signing a 4 star OL certainly doesn't guarantee he will perform well enough college so as to be invited to the combine, but the odds are better at 28%. So basically a little better than one out of every four 4 star OL should play well enough to be invited to the combine. The sample size for 5 stars is so small that the results might not be meaningful year-over-year. But in 2015 there were four total 5 star OL recruits, and four years later in 2019 there are five 5 star OL invited to the combine.
So where it comes to the OL, stars seem to matter if one accepts the a combine invitation is a good proxy for college performance.
Misc: There were also six 2 stars and 6 non-rated players invited to the combine. I don't know the universe of 2 stars and non-rated players so I didn't do the same analysis, but I'd expect the probabilities are minuscule.