It's what you can't see that matters.
Sure it can be wirebrushed, fibreglassed, Dinitrolled and undersealed to get a couple of years protection an Mot pass, but you can't readily access the chassis frames next to the cats behind the heat shields with the exhaust in the way.
Obviously, the remote diagnosis will always default to the worst case scenario, but if you've owned a rusty Omega then you understand that what you can see is always the tip of the iceberg.
That £2,500 43,000 mile Estate on auto trader being a case in point.
Looked fantastic, MoT fail last week suggests it needs new sills, front rails and a floor pan just to pass, and that's notwithstanding of the various patches it's had for previous Mots.
It will always be worse than it looks.