1 Obi-Wan: And these blast points, too accurate for Sand People. Only Imperial Stormtroopers are so precise.
2 Luke: Wait. Are they accurate or precise? Or both? Those are two different and independent things.
3 Luke: Accurate means to close to the target, whereas precise means repeatable with low dispersion.
4 Obi-Wan: Luke! Don’t rant about technical definitions in a fictional story! It’s too dangerous!

Anyone who's done a science degree knows the difference.

Taking Obi-Wan's statement at face value, it could be consistent with the observed efficacy of Stormtroopers in the Star Wars films. Sand People could be very inaccurate, so Stormtrooper fire could appear to be too accurate, even if still not very accurate. But Stormtroopers could still be more precise than any other force - they consistently miss their target by the same distance and direction - so Obi-Wan's statement that nobody else is as precise can also be true.