I've bought two Approved Used that required work before handover.
My approved used CLS was "good to go" from the forecourt , once it had went to the bodyshop to have an obvious scratch repaired and a sunscreen handprint removed from the rear quarter.
FWIW a 2016 vehicle should possibly have minimal underbody corrosion , depending on where it has lived for seven years , let alone enough for it to be rejected at point of sale.
K