I think, possibly. I don't have that specific device, but if you were using Equalizer APO and doing the EQ there would probably make sense to have it flat. I think can can chain, like you could have Equalizer APO doing the EQ first and then have the Sound Blaster doing further processing, but generally preferable just to do the DSP in one place I think to keep it simple.

People seem to use it with that, there are even some specific handling software for it:

/r/SoundBlasterOfficial/comments/v2yjve/soundblasterx_g6_issue_installing_equalizer_apo/
/r/SoundBlasterOfficial/comments/dyr2nw/improve_sound_blaster_headphone_audio_for_free/
https://github.com/heftyy/sb-output-controller