I never noticed it before but yes, it seems to be normal. It's not related to the TX Filter in the PHNE radio panel. It might be savable as a profile. I notice when I set 40 meter LSB to 0, I'd jump to another band and LSB was at 100. Then returning to 40 LSB was back to 0. So maybe it's not a profile but persistence.
Is there value to SSB signals between 0 and 100 Hz or does it waste power while adding nothing to intelligibility?