My 3* are generally about 69-72 overall. Maybe you got unlucky? The Top 3* I have ever nailed is a 78 overall CB. He was a 88 by Junior Year.
And for 4*, 68 is the lowest I've ever seen, most of mine start at about 74. My top 4* was a 79 pverall QB (90 Junior Year). Players who play a lot seem to progress more for me, so a Freshman Starter will progress faster than a Frosh Backup, I believe. Red Shirts I have no clue how quickly they progress.