The point of the sentence I quoted is simply to differentiate “regional territories” from “colonies”. Regional territories can trace a line through contiguous original territories back to the capital, while colonies are removed from the capital. The only difference this really makes is that colonies of minor powers are handled a little differently than their capitals. Since minor powers don’t have regional territories anyway, this sentence is more about “flavor” than anything else.
Another big question
If Britain liberates Belgian Congo from Germany, is it captured like any other territory or is it returned to France because Belgium is aligned with France?
Q. If a friendly power liberates a minor power aligned to my power or one of its colonies, who takes control of the territory?
A. The power that captures it takes control. Minor aligned powers and their colonies are not original territories of the major power the minor power is aligned with, so they are never liberated.