On Game page, it states that:

"Embark upon a journey with up to three companions as you bend the very fabric of time, where what seems like the case of a simple murder unravels into hours of quests facing fiendish foes, magical polymorphs, and dastardly bosses."

However, we can have up to *four* characters so up to *two* companions. Possibly a typo or is it a spoiler?

I think it is just grouping one of the Source Hunters in with the companions / henchmen to put the reader in the place of a Source Hunter, rather than a more precise but less personal tone of saying something like 'with 2 to 4 characters'.