The HIG mentions that redundant words like "Enables" or "Activates"
shouldn't be used for tooltips of boolean properties. In this case
"When checked" was the redundant language that was implied by
the checkbox itself-- convention is to just state what the property
does when it's on.

Also change a few conjugations to the imperative and simplify
wording slightly, in order to be more consistent with language
elsewhere in Blender, and to be a bit more direct.

https://wiki.blender.org/wiki/Human_Interface_Guidelines/Tooltips