Summon Shadow does not function like a normal summon

[Diz-e]

Summon Shadow (from the spell Shadow Conjuration, cast from spell slots) does not function as a regular summon in regards to summon pool/summoning points, nor does it combine with other summons in your personal party. It completely dismisses all other summons and/or undead animates when cast, reducing the usefulness of this spell drastically.

Can this be fixed? Otherwise, it's no wonder that no one uses this... and it's a real shame.