"Pseudo" means false. "Vague" may not go all the way to false. It may just mean not thoroughly explained.
Interested in Language
Instead, Target, as well as grocery stores, shopping malls, greeting card sellers, clothing retailers,
and other firms, tried to peer inside consumers’ heads the old- fashioned way: by hiring psychologists who peddled vaguely scientific tactics they claimed could make customers spend more.
As I understand it, the meaning of the phrase would be phsycologists used pseudo-scientific tactics.
Is it right?
There may be a veneer of science to what is otherwise opinion.
MikeNewYork, SotthingDave, thank you for explanations!