It's both, but there are metrics now with Statcast. You can go to Baseball Savant or Statcast and tinker around with the release point data on your own. It gives you a grid and shows where pitchers release the ball, and you can also get the numbers and compare various pitchers. All of that is publicly available. Takes some patience. But it's fun. Scouts add a layer to that information about what it looks like person, what it looks like to the hitter, and so on.
I'm not sure if you'll see a shift in "arsenals," not any more than you're already seeing over the past few years as spin rates took hold, more curveballs are being thrown and so on. We will see changes to how arsenals are used, and how mechanics are adapted to utilize tunneling. There are many pitchers who have been doing this for several years, honestly.
A quick story: Wainwright started elevating his four-seam fastball and his cutter at times over the past few years for this reason. It plays off his curveball. It comes at the same eye level and it throws the hitter off, and he took some lumps finding that but now benefits from it. Look at the called strikes he gets as a result of being able to throw that curveball and fastball from the same release point and seemingly, to the hitter, to the same spot.
It can work long term. There are myriad of release points. You're discussing an arm swing, I believe, with Wacha, and that is something he's had to address, obviously. Kudos to him for all the work he's done to strengthen his arm and do what he's doing for the Rays.