A bit late to the party, but I think it's better to reply here instead of opening a separate topic.
I returned on Christmas and stumbled into this exact trap. I considered it a bug, hence I contacted the Support via a ticket. The responding GM referred me to a forum post, stating that it "works as it should" and "it is intended for new and returning players".
Since they didn't make sense to me at all, I emphasized that I am a returning player, to which a Senior GM responded. The Senior told me something about new characters and whatnot, and that they are not the Dev Team, almost as if they didn't even read my ticket. Eventually they closed it (twice), since "we got nothing more to add to this". There are more details to the story, but it's already becoming lengthy. Conclusion: Instead of explaining to me how the Soul Boost works, they left me in the dark and I got muted.
Since "works as intended" usually means "we won't change it", here are some tips for the NC staff on how to handle an (due to the lack of in-game information) obviously confused player better:
1. "It's the Dev Team's, not our business" is not helpful. Rather provide the player information on how the SB works, e.g. a link to corresponding patch notes.
2. "You don't need to complete all missions to be able to claim all rewards", "even if a stage isn't unlocked yet, you can already work towards its mission completion", or "Soul Boost will return with a new season after the current one ends" are just 3 examples of what a GM could tell a player who is reaching out to them. Which brings me to....
3. Don't leave someone looking for support uneducated after telling them nonsense that has nothing to do with their issue, and muzzle them by closing their ticket. That could easily be considered rude and unprofessional.
From my point of view, Soul Boost is a great addition to B&S. However, the lack of in-game descriptions can make it difficult for newbies and returnees to understand it from the get-go - even more so, if the NC Support refuses to provide proper guidance when being reached out to.