It's only to reduce bloat in the guidecam, so even if it does half a job, it's half of something
I use one in front of my Baader LP filter on my CCD. I thought at first it was causing internal reflections so I took it off and tested, and no different (somewhere else).
Only issue I have with the SVBONY is they aren't stackable. You have to use them as the last filter on top of a stackable like Baader, Astronomik etc.