No, it is not a good example. MCW was the 4th guard. So, yes, in JBs system his 4th guard no matter how good won't get many minutes.
But Roberson should be the 3rd forward, totally different. The 3rd forward can get significant run. JB does not use a 6 man rotation very often, and yet he did it instead of sending Roberson out there one time. This is not a JB always does this thing, it is he feels Roberson is not ready thing.
And for those who are claiming Roberson is ready, they are doing it based off a lot less information than what JB has in front of him.