So... long ago and far away, when I first started reloading with a Redding M25 turret press (pre-cursor to the T-7), I bought a couple sets of the Redding Comp shell holders (.223 and .308) to go with my various Redding Comp die sets. As a new reloader I was somewhat terrified by the thought of trying to adjust such a tiny amount on the die body of a 7/8-14tpi die, where a mere 1/8 turn is a little under 9 thou. Kept using them on through moving to a Redding Big Boss press, and then when I got a Forster Co-Ax, I immediately bought the conventional shell holder adapter so I could keep on using them.
At some point... it became a bit of a PITA, and I wasn't getting quite what I wanted out of the Redding shell holders - one of those times where one shell holder was getting me about 3 thou bump, and the next was getting me more like 0 to maybe 1 thou, and for whatever reason, I wanted *two*. No more, no less. I was a little more confident by then, and tried adjusting the die lock ring. Made a scratch on the ring, and moved it about one letter width of the engraving on the die body - which got me exactly where I wanted to be.
Eventually, I just ditched the shell holder adapter, and went back to the original Forster spring-loaded jaws, and life became even easier. I just adjusted the die where I needed it to be, and sized on. If I needed an adjustment, I just made it - I wasn't constrained to the steps/increments of the shell holder set, or felt like I needed to file/grind one down to make some DIY custom height shell holder. And I never again had the little 'problem' that nobody ever mentions... where you size one caliber/cartridge with one shell holder, and then go to do a different caliber/cartridge (same head size) and forget to change the shell holder. Whoops - there went your precious headspace, oh no what will you do? And to those who'll claim they've *never* made that mistake... sure. Whatever you say, man
Never had an issue with keeping my headspace where I wanted it either. It all just worked.
Later, I bought an Area 419 Zero press, and went 'all in' on their system, with the shell holders and solid die contact with the shell holder / ram. TBH, I had more *problems* with that setup than I ever did with the floating dies in the Co-Ax. So eventually I sold it, and went back to the Co-Ax - and my 550 - for my sizing needs. Neither of which use the fancy stepped shell holders, and still manage to keep my case headspace where I want it.
I realize there are some special circumstances where people are firing and sizing cases repeatedly, without the ability to anneal every firing (like during a BR match) and feel they need to be able to adjust their die headspace *exactly*. I would imagine something like the Whidden click-adjustable die rings would help with that... but a) I'm guessing most of those folks aren't lugging a Co-Ax to the range for those events and b) the slot in my Co-Ax was pretty snug to where I wasn't happy with the function of those rings on my dies in my press. Maybe the fancy die rings from Forster or SAC that have laser-engraved hash marks on them (why that took so bleeping long to come to market is a crime) would be of use?
YMMV.