Does the deceased stop moving, despite the will of the coffin bearer, when "Lā ʾilāha ʾillā Allāh" is uttered, or is this a false belief?

The basic principle is that the deceased do not address the living to command them to stand in a specific place, or to recite a particular dhikr and then order them to proceed. This is because these are characteristics of the living, and there is no evidence to support such claims.