A-lot of guys shoot at the bull to try different loads and sabots and the post are of how they shot and grouped. When one is finally sighted in on a bullet powder combination that they like, then they go for the center bull to make final adjustments.
Say you have sighted in at 40yds and your in the bull, then you may sight in for 100yds. So after your sighted in at 100yds you may go back to 40yds to practice, when you shoot at your 40yd target and your sighted in for 100yds your groups will be a couple inches high of the bull but still tight.
I personally never post a target group untill Im fully sighted in and my groups are tight, 1" or so. They may be high in the Bull, but there still tight and it looks better than a group off to one side or the other or high or low.
Again, most post of groups are to show how a ML shot with a specific load.
(BP)