While pressure is the big contributor, I wonder if clearances are the cause of loosening pockets.
Clearance for the case body at webs, and bolt cone to breech.
It's common for some reloaders to see pockets loosen without 'pressure signs' they've come to recognize. But there is a 'pressure problem' sign that is less commonly recognized: Diameter growth at web-ring.
Sure people see it once to a point of poping extraction. But if chronic growth is occuring and masked by big sizing at webs, well then there may still a price for this even if exraction is fine (no pressure sign).
It may not be simple as brass brand and pressure.
But then, Lapua is harder, and I've found that pockets in factory chambers last longer with Lapua over Norma.
I found this article interesting:
X-Ray Spectrometry of Cartridge Brass within AccurateShooter.com