That's no BS there. I have had some Hornady match with ejector swipes and heavy bolt lift. Not saying this is what you should do, but every rifle and every load of mine have always ended up above book max.
Altus built both the 6cm and 6.5cm, I also have a few that Travis from TS built, and a couple from Moon at Crescent customs. All 3 shops do amazing work. I do all the cerakote work on them now though.
Wife and I had a chance to hunt a friends property this year, and I'm glad we did. Both of us were just a week out from recovering from Covid and I'm glad she agreed to go. Hope everyone else is having a good season thus far.
I personally prefer Rl16 in my 6 and 6.5CM over H4350. I have also found that I prefer RL26 in my magnum stuff over H1000. H4831 is great powder for both calibers, but you won't be setting any speed records with it.