"Alvarezsauroids were originally considered to be a group of flightless birds, but it is now widely accepted that they are not nested within Aves (1–3) and instead represent a basal maniraptoran lineage."This quote does not make the necessary distinction that I have been emphasizing. Namely that the word "maniraptoran" is not precise enough.
We need to distinguish between Aviremigia on the one side and dinosaurs on the other.
Alvarezsaurids are members of Aviremigia. They are primitive birds.