Paul,
As a general rule, there is no general rule which applies to handloading. Logic also frequently does not apply either.
There are many dynamic issues when considering cast vs jacketed bullets. The hardness (strength) bullet introduces a variable which prohibits making any general statements concerning velocity/pressure. Whether we are talking about a rifle, fixed chamber (single shot or semi-automatic) pistol or revolver is the other variable. For the fixed chamber guns the assumption you make usually holds true within close enough pressure variation that it is usually a safe assumption, especially if the loads are somewhat below absolute maximum. With heavy loads the accuracy will generally go out the window with cast bullets before safety is an issue, assuming modern guns designed to operate in the 40,000-60,000 psi range.
When we get to a revolver, the variable of the barrel-cylinder gap and forcing cone come into play. It has been demonstrated by authorities in the field having proper est equipment, that the cast bullet will frequently yield a higher pressure that the jacketed due to its bumping uo in the forcing cone and then being swaged down as it enters the barrel proper. This can happen at any time the load develops pressure sufficient to bump up the bullet which varies based on bullet hardness. This bumping up is usually what causes cracking or splitting of the barrel shank/forcing cone. This is also the reason a revolver can be severely damaged by trying to load hollow-based wadcutters to too high a pressure level.
What this all means is that with hard cast bullets your assumption is usually true, but you cannot always be sure with bullets of unknown strength characteristics.