Sobers was initially picked for bowling IIRC.
And when he was, as you say, a "specialist bowler" this is the period where he was bowling with Gibbs, Hall and Griffith.
This is where you got it wrong when you said when he was the 4th/5th bowler he wasn't good. Because this is the precise period he
was good.
Sobers should not be questioned on being great - there is nothing that can make him a great bowler. The question is how good was he if he wasn't great? Now you can gauge that for yourself. I encourage you to read the Keith Miller vs. Gary Sobers thread to see the arguments and the counter-points. But I warn you, if you come to the same conclusion as me...well...some people don't like believing Santa doesn't exist.