It's also stated that Qin Shi Huang could smite Chaldea whenever he wants, and he nearly did with the Great Wall if not for Spartacus's interference
before you say Spartacus is only High 6C, Crying Warmonger is specifically designed to become stronger depending on how strong the attack he's counterattacking is, meaning he buffed himself to Low 1C in order to stop it.
Before you say that that's a stretch, several other servants in the series have launched Low 1C attack at the cost of their own life, like Arash did in the Sixth Singularity in order to stop Tituria's attacks. This shouldn't be treated as any different
Not to mention, think about it: If Qin Shi Huang was literally just an immovable blob who could only use High 6C attacks, Chaldea would have never felt threatened in the first place since they have their own Low 1Cs. Chaldea explicitly stated that Qin Shi Huang, as well as Lostbelt 4 as a whole, was the strongest force they faced at the time, which would include the likes of Scathach Skadi, who's Low 1C by herself, Surter, who can stomp Skadi, and Ivan, who's also Low 1C. If Qin without his human body is only capable of launching High 6C Attacks then none of his statements would make any sense