It is normal for surveyors to cover themselves against problems being found which they were not allowed look for. For example, if the house had fitted carpets and the owner will not allow the surveyor to lift them, it would be reasonable to say so in the report. Similarly, if a house is furnished and he is not allowed move any of the items of furniture it is reasonable to state this. It all depends on what is reasonable in the circumstances.
We would expect a surveyor who gets reasonable access to a house to be able to express a firm view on the overall structure. It is much more difficult to express a firm view in relation to drainage or wiring. A surveyor can flush a toilet and see that the drains seem to be flowing freely but with an old system this does not mean that they will not give trouble.
It is also difficult to test the quality of electric wiring. The surveyor can look at the fittings, but this is just a basis for deduction. The fittings or even the fuse box may have been replaced without the wiring having been upgraded. A surveyor is unlikely to save you from problems with wiring or drainage for that reason.
Exclusions should make practical common sense in the light of your discussions with the surveyor. If you feel the opinions are unfairly qualified, you should talk this over with the surveyor or seek the advice of your solicitor, who will be impartial and who will be able to express a view on what is fair and reasonable in the circumstances.