Maybe the projectile has attitude control based on programmed range? Would be interesting to see some design specs on the projectile.
My understanding of the projectile functioning is this:
1. barrel rate of twist is known with precision and it matches the ro of the fired projectile
2. projectile has internal sensor that logs each 360 rotation
3. rotation number logged therefore indicates projectile distance traveled
4. intial range determination (and subtration or addition of desired detonation point) marks rotation number at which projectile is to detonate
5. projectile detonates when match is achieved between metrics for designated rotation mark and distance traveled.