Maybe for a server - regularly update the package list and compile a list of packages needed to be upgraded. Then send the list to an admin and let them do the update, so that it isn't unattended.
upgrade upgrades only installed packages, and only when it can do so without adding/removing other packages. dist-upgrade will do the same, plus upgrade packages that have dependency changes. If package A v1 depends on package B, but package A v2 depends on package C instead, using upgrade will keep your package A at v1, while dist-upgrade will install the new dependency and upgrade package A to v2.
full-upgrade is dist-upgrade, it got renamed because of the possible ambiguity (one could think that it upgrade your distribution, like from debian 11 to 12)
If you want to install something, do you wish to just update before hand, or to upgrade too ? I guess the former.
Now you could add update to the install function, but it would mean if you updated 5 mins ago for install something, you would need to update again as you install something else.
Better to keep them separated and call them as you wish.