Does (High) Sierra set a higher bar for menu bar apps? Previously with El Capitan, an app such as smcFanControl (2.6) could furrow in an obscure way into the OS.

Has something changed in either Sierra or High Sierra? After sleeping and waking up, the same app (in the same version) now requires re-entering the sudo password, or otherwise it fails to run in the menu bar.
It has nothing to do with a (perceived) "higher standard" for menu bar icons, it has to do with the privilege level of the process you are attempting to run (or restart from sleep).

In this case, to access the process that controls the fans, you need to have root level privileges.  Until you grant those privileges to that process, it won't run and thusly won't show up in your menu.