Last I saw the claimed matching range of Tuner Genius was minimum 3:1. Keep in mind that just because a tuner may capable of matching a higher SWR load does not mean that it will match any load showing that SWR. It depends on the characteristics of the load: band, high (>50 ohm) or low (< 50 ohm) Z, resistive or highly reactive load, etc. Most tuner specs are based on resistive loads, so don’t mean a lot in the real world.
The MFJ 998 specs show a matching range of up to 32:1 SWR for loads over 50 ohms but only up to 4:1 SWR for loads under 50 ohms. Note the “up to”. Throw in significant reactance and those matching ranges will decrease. For example, my LDG 1000 has a claimed 10:1 matching range, but my 160M dipole has a freq. range where the LDG can’t find a match at even a 3:1 SWR.
To me the big advantage of the Flex tuner is integration with the Flex amp and radios via LAN. I don’t expect a wide matching range at high power with a switched inductor/capacitor tuner like this.