I'll probably get some howls of outrage but I don't think any such finessing a sizer that way will make any measurable differencee for you. Just the fact that you're using threaded dies in a threaded press suggests that your loading precision and your rifles and scopes aren't at competitive BR level so any potential improvement will be lost in the noise.
Keep doing what you're doing. If you want optimum accuracy from each rig work on load development for each rig and don't sweat over such precise shoulder placement.
Not a "howl of outrage" as you suggest, more a holy schitt you have no idea what you are talking about
First off most (not all) benchrest shooters use a threaded die for full length sizing, most if not all use some type of arbor press for seating.
precise shoulder placement is a good thing and worth the sweat, about the only thing you dont have your head up your azz on is load development.
I use shims on both sizing and seating dies.
