There is a useful old discussion on this forum with many authors, which helps to better understand ArM5 p.84: "Mystically, the Arcane Connection is still a part of the target, thus making the spell possible." Access to such threads makes the retrieval of this forum so very valuable.
We find there:
In particular, an AC to the caster is not necessary an (ArM5 p.112f) Part of her, or can be targeted by her using a spell with Range (ArM5 p.111) Personal.