I've only ever seen Sean on Ibanez fretted and fretless basses. I listened to Cynic back in the day but only recently got to know him better. RIP by the way. His choice of EQ/sound is such that his fretted bass sounds extremely similar to his fretless. Same boosted mids sound.
Here he plays both basses and it really sounds like the focus sound.
Do you think he used Flatwound Strings?