Lapua has all sorts of ballistic resources and I have noted that they came up with a 6.5 mm bullet vs. a 6mm for the 6.5X47 Lapua.
The 6.5X47L was designed specifically for one discipline, northern European 300 metre ISSF / CISM 3-position shooting. 300M ISSF is very big in Scandinavia and some continental European countries attracting big money (by Europe's standards) sponsorship and gets lot of media and shooter attention. (Nearly all of their non-military ranges are 300M too, have concrete floor / covered firing lines, and have been e-target equipped for many years now, so ideal for this discipline.)
When Lapua designed its new cartridge, the 6 Norma BR dominated ISSF. Lapua wanted very badly indeed to have a cartridge bearing its name seize that crown! In 2019, 6mm Norma BR dominates ISSF! Fortunately for Lapua, its cartridge does other things at longer distances rather well.
ISSF's needs set the specification for the 6.5X47 - 6.5mm to match 105gn 6mm external ballistics at modest pressures and velocities, but provide a large increase in barrel life over the 6 BR; precision that at least matches the BR, ideally improves on it; as small a case / charge as possible in order to again maximise barrel life and also to miminise recoil which would nevertheless inevitably exceed that of the BR.
The reason for the barrel life priority is that ISSF is an extremely demanding discipline which requires constant and frequent practice sessions in each position to get to the top and stay there, and its courses of fire see a lot of rounds downrange, so a big tournament will see hefty ammunition consumption.
The very top competitors are factory sponsored and get factory match cartridges and no doubt new barrels too so the barrel life issue isn't an incentive to change for them and I imagine that on balance the 6.5's recoil increase, even if modest, tipped the balance away from the Lapua cartridge. With very small 10 and X rings, the kneeling and standing stages are very, very demanding and overall shooter fitness and avoidance of fatigue essential.
An interesting issue and story, but not one to use in an argument for 6.5mm v 6mm calibres per se.