I thought that was related to the Polarity, not the frequency. To visually describe what's going on for me, is that even if I increase or decrease the frequency offset, the line doesn't move at all.
I'm pretty sure that it's not a problem with the polarity, as frequency still doesn't work if polarity has been locked onto 100% output data.
Edit: never mind I'm just stupid. I think I've figured out how it actually works. Thanks for giving me advice all the same.