From aptitudes man page

Upgrades installed packages to their most recent version. Installed packages will not be removed unless they are unused (see the section “Managing Automatically Installed Packages” in the aptitude reference manual). Packages which are not currently installed may be installed to resolve dependencies unless the --no-new-installs command-line option is supplied

While it wasn't totally accurate it is reality that it will NOT remove packages. Also the phrase "Packages which are not currently installed MAY be installed to resolve dependencies ..." Does not say they WILL be installed. Apt is not perfect and I have seen instances where packages that are not removed cause problems I have also seen cases where dependency issues are not resolvable easily so nothing new is installed.

Anyway your initial question is not actually a question instead it is a statement so I am wondering what your point really is.