The Lemegeton's own table of contents calls Book One a Book of evill spirits. Vassago does not read like one.
The entry describes a spirit of good nature, who declares things past and things to come and uncovers what is hidden or lost. There is no menace in it, no warning, and no demand for offerings. The same is true of several other entries: Seere is described as good and indifferent in nature, Orobas as faithful and unwilling to let the operator be deceived, Marchosias as a truthful answerer who hopes to return to a heavenly rank. Andras, at the other end, is said to be lethal.
This is not an inconsistency so much as a fossil of how the list was made. A catalogue of spirits with named offices, teaching, finding, transporting, healing, belongs to a tradition of ritual magic that did not sort its entities into the good and the damned with any consistency. The framing of the whole set as evil spirits bound by Solomon is a wrapper placed around that catalogue, and the wrapper does not fit every item underneath it.
Weyer, whose list is the ancestor here, was writing to argue that this material was delusion, and his catalogue reads as an exhibit rather than as a manual. The Lemegeton's compiler took the exhibit and re-presented it as working material within a demonological frame. Entries like Vassago's show the seam.
The practical consequence for a reader is that the moral vocabulary in the Goetia, evil, good, indifferent, obedient, faithful, should not be read as a system. It is inherited language, applied unevenly, in a text with at least two purposes layered on top of each other and no author to reconcile them.