It's an objective statement of their tactics, not something relative.

Modern precision guided weaponry is meant to selectively destroy military targets. WW2 style strategic bombing was targeting civilian populations mostly trying to disrupt industrial production in support of military action. Randomly firing a few unguided rockets into civilian population centres can't possibly achieve either. The only goal is to provoke terror in the civilian population, therefore it's a terrorist organisation.

You can see similar tactics in the "human safari" the Russians are running in several Ukrainian population centres.