The warning certainly isn't new, although maybe rephrased. Similar warnings from them regarding factory 30-06 in the past. I wonder if there was an "incident".
I don't quite understand the bullet weight warning though, unless the context is factory ammo or an attempt at a "catchall" statement. Sounds like a general CYA warning in response to an incident. I'll have to check for sure, but I think the M1icon booklet they ship with the rifles has a similar warning regarding factory ammo and hot loads.