There are. They are instance methods of a group or component definition’s Entities collection (where they should be.)
Visual Basic for Applications is not Ruby.
You need to understand that every big fan of every of language other than Ruby, has come into every SketchUp forum there ever was, and disparaged Ruby and the SketchUp Ruby API,… because it does not do things the way their favorite language does.
Ruby does things the Ruby way. And the SketchUp Ruby API is no more than an extension to the Ruby objectspace. (To be effective more quickly, requires a coder learn basic Ruby first.)
ADD: Usually, when someone comes into a Ruby API forum, waving the flag of another language, saying that Ruby and the API does not do things correctly,… well that will upset some of us a little bit. But we are somewhat used to it, as it has happened so many times in the past.
This can also be done. Such operations are programmed using the API’s Ruby Tool class.
Also new for SketchUp 2016, are two selection wizard methods of the PickHelper class:
In Ruby, a “handle” is called an object reference.
A “name” is a designation of an built-in attribute (property) of both instances and definitions, which is gotten or set via methods identified as name() and name=(). (Ie, instances can have a different value for their name property, than their definition has.)
Which also exist. It is standard in geometry to create and apply transformations.
See the APi’s Geom::Transformation class.
The Group and ComponentInstance classes have these instance methods you speak of.
But are not limited to “simple”. They have the full power of whatever transformation the coder creates. (If they were “limited”, we would be bitchin’ for more power. 
)
Mirror ? There are plugins to mirror objects that might help. But this operation usually needs user interaction, so it is programmed as a Ruby Tool class.
This is an instance method of the Sketchup::Face class.
see Face # followme