[ deleted ]

Class Unity - Scripting API: HandleUtility contains geometric methods, but all of them are strictly tied to the mouse. Why couldn’t they create some class like GeometryUtils so that it would be possible to use not only the mouse but also to check for collisions of geometric figures. Using that only for the mouse is somehow excessive.
As far as I know, HandleUtility class appeared recently with Unity 6.

Uh, it’s been around since Unity 5.2 according to do the docs:

Yes, it’s strange that it’s not highlighted that there is support in older versions. Although in fact there is.

What do you mean by highlighted? The docs tell you every version a particular part of the API is available on.