The term effective isn't used anywhere in the book to refer to directly augmenting an attribute - the terms used for directly increasing a rating are "adds its rating to" or "increases _________ by". Anything that adds a numerical bonus to an Attribute makes a direct and explicit reference to doing so, Power Focus makes no such reference because it does no such thing.
-- SR5 uses "effective" for directly adding, modifying, or substituting attributes in four spots (I didn't check SR4 books).
Magic Fingers: The hits on the Spellcasting + Magic Test become the spell’s effective Strength and Agility.
Chisel/crowbar: The chisel (or crowbar if you prefer) doubles your effective Strength when you’re forcing a door or container.
Explosives: Each hit on a Demolitions + Logic [Mental] Test adds 1 to the explosive’s effective rating.
Power Foci: They are very powerful foci that temporarily increase your effective Magic rating.
-- This isn't complex technical writing. You're flat-out inventing a distinction for power foci.