I think that point 2 means the velocity achieved is related to the pressure developed, not the quantity of powder burnt, while point 3 means that some rifles may develop maximum acceptable presure without reaching the advertised velocity, as would be the case if the published data was worked up in a 24" barrel, and your gun has a 22" barrel. Differences in chamber tolerances, barrel and rifling form, bullet shape and construction add infinitum, can change the relationship between pressure and velocity.
The point is velocity won't damage the gun, pressure might.