By your measurement the full length sized case grew .002 with the +.010 competition shell holder.
Try the +.008 competition shell holder and see if the case becomes longer.
Keep going with shorter +.006, +.004 etc shell holder to see where the shoulder moves.
You may have to fire the case several times and only neck size until the case becomes long enough to cause effort closing the bolt.
Below your case "MAY" become longer if you size the case more and reduce the case diameter more. This depends on your chamber and dies, example a fat chamber and skinny die will make the case grow in length more.
The case shoulder location on new rimmed and belted cases is not critical because the case does not headspace on its shoulder.
Below a new .303 British case in a Wilson case gauge and this case is still not resting on its shoulder. And the rim is stopping the case from dropping further into the gauge, and the case shoulder was actually 1/4 shorter than the chambers shoulder.
And below is a fired case in the Wilson case gauge and the amount the case is sticking above the gauge is how much longer the British .303 Enfield chamber is.
The British used cordite powder that looked like long strands of spaghetti. And the powder was loaded into the rimmed and belted cases "BEFORE" the case shoulder and neck were formed. So the case shoulder location was not critical if shorter than the chamber.
Below a new and old rimmed .450 Martini cases, and you can see how crudely made the older case on the right is. Bottom line the belted case is a old British design and even today the cases can be much shorter than the chamber.