assembly features such as extruded cuts in assembly not transferring back to part model

Hello All,

Just a general question regarding the reverting of assembly features (i.e. extruded cut) not reverting back into part itself.  I am fairly new (~year experience) to the assembly aspect of SW and just wanna confirm that any changes (such as an extruded cut of a shaft going into a weldment) will not transfer back into part.  I thought I remember reading in one of my books that its only a one way street (part model changes affect assembly model but not the other way around).  I have an assembly where there is a weldment and another part mated together and I would like to make an extruded cut of a shaft by converting the entities of the diameter where it passes thru the wall of the weldment to clear (make a hole in wall of weldment to allow shaft to pass thru).  I am able to do this, but when I look at the weldment part itself in its own file, the hole that was "extruded cut" is not there, it only is present in the wall of the weldment in the assembly file.  I think this can be considered "Top Down" assembly modeling and what I'm looking for isn't possible.  Just looking for a quick confirmation.  Thanks!

SolidworksAssemblies