My bad, I missed the part about it being printed concrete, that would explain why the crack has gone through the "blocks". No I don't do any printed drives.
Fair play, they have done a cracking decent job of the texturing, (fooled me) it is a bit of a shame that they did not show the same diligence on the structural integrity. Maybe 6 to 8" was not that much codswallop although I do think 8" is overkill on decent well compacted type 1 formation.
I still stand by my comments about the stress lines being parallel to the trench, and any movement in the foundation would be toward the trench.For the concrete to crack perpendicular (and the length of the crack) to the trench would suggest something has driven over it or there is a line of structural weakness in the concrete or the formation for the slab to fail,
Whilst the VM works may have been a contributing factor I do not think it is the primary cause. It would be interesting to see what happens.