I ask because of a conversation that I had with an Anschutz employee a few years ago and some follow up conversations with a respected reamer maker and a nationally competitive rimfire shooter.
According to the Anschutz employee, Anschutz uses reamers that work best with Eley. They have a particular leade angle, headspace and perhaps other dimensional aspects of the reamer that are optimized for Eley.
The possibility of designing a reamer that is optimized for a particular LR cartridge was confirmed by both the reamer make and the competitive shooter. Both said that they understood the concept and the competitive shooter said that he did this.
If you look at pix of Lapua X-Act or Midas+ and then look at pix of Eley Tenex you can see that the shape of the bullet and thus where and how it would engage the leade differs. Perhaps this is analogous to varying seating depth on a centerfire rifle bullet.
Lapua X-Act
Eley Tenex
Granted, these are adverts and not blueprint type drawings with checked dimensions, but they are perhaps enough to illustrate my supposition.
The reason I investigated all of this was that I was about to put together a rifle for NRA Smallbore Rifle Silhouette and was planning to use Lapua ammo. I was somewhat disappointed to find out that the barreled action I was most likely to choose, an Anschutz 1907-U6, was probably not going to like the Lapua ammo I wanted to use.
It seems that, as I inferred from your post, the greater efforts Lapua has been making recently is producing results. and the the long time king of rimfire ammo is being legitimately challenged.