Hey! Yes the voles do have penalties on their stats because they get stronger Boons. Having them be at a disadvantage with rolls to have better boons for their team was intentional.
Also, the alternate player species are supposed to be a challenge compared to playing as a mouse. They’re not to stand in as races like in D&D, where they have comparable pros and cons. ALL alternate player species are more difficult than playing as a mouse. The vole with its negative stats, and the frog & lizard in that they can’t normally communicate with rodents- you’ll need a book to do so.
Hope this helps.