More on getObjectExtent()

The wording says "[...] The bounding box calculation is based on the
abstract locus of the primitives within the APS."
What does 'abstract locus' mean?
 
I'd like to know if getObjectExtent() returns a tight bounding box on a
given APS. i.e., given a polybezier, are control points part of the
bounding box calculations or not?
 
Benoit.