While it’s doubtful that a an hour long pre purchase car inspection would have picked up the head gasket issues on my 2005 Subaru, undoubtedly the mechanic would have noted the dried coolant spills. And possibly pointed out the age of the pipework on the radiator, maybe even zoomed in on the cracks I didn’t properly look for and note that ‘these will need to be replaced.’ Plus their fault code reader would have had the settings for Subaru, where as mine doesn’t seem to know a Subi if you threw it at them (it’s more Subi software being a little more out of the ballpark than most generic readers it seems.)
Would I still have bought it knowing the faults? Maybe. Possibly. Especially if I used what was found in the pre purchase inspection to lower the price. But then I’d also run the results past someone with more knowledge in these things that me. Regardless knowing what I know now, I’m not buying another car without one..