Missile ranges are pretty much whatever the manufacturer says they are. Two missiles with two different ranges can easily be apples and oranges.
Case in point: Aster 30. Manufacturer says 120 km in most brochures. Then in one brochure there's a more detailed rundown where it says 120 km is against slow flying object and against a jet fighter it is more like 70 km.
Buk family. It's made to engage fast approaching enemies and goes directly towards the threat, through shortest trajectory possible. Its range against jet fighters is in 40ish km range. It has enough kinetic potential to go farther, if guidance allows it. Buk m3 comes and it suddenly it has 70 km range. (the missile itself was changed too but not that much)
Perhaps biggest examples are SM1 and S300 families where exactly the same missile achieved greater ranges with different trajectory use. But one needs to keep in mind that the additional range may not applicable against all target types. Fast, alerted targets may still need to be engaged through trajectories not allowing maximum range.
S300 used the same missile and changed guidance to go from 50 km to 90 km range. Later variant of missile then started off at 150 km and is now at 250 km reach. Against *unknown* target types. Most likely slow, unalerted targets.
Peculiarly enough, the fd2000 range of 125 km was specifically mentioned against jet aircraft in one of the manufacturer's brochures, and another one had a graphic of jet fighter drawn as the 125 km target.
It may not mean anything but artist's liberty, of course, but it is also plausible that apples to apples reach, when compared to s300 for example, isn't 250 km vs 125 km but a different set of figures.