Remember ALL laws, rules and procedures are simply written by normal people - they are not the word of God! As the IRE standards were probably written before GPS coupled autopilot & FMS tech was good enough to fly the approach, then your answer is simply "As the rule is silent, it's down the to examiner's interpretation and good sense."
The purpose for the test is to see that the pilot can conduct a safe approach. If the pilot is a professional, pretty much ONLY flying one type - then yes, it is perfectly valid to watch them fly a safe approach in that type using the tools available (and the pilot still has to interpret the needle, to monitor the approach).
If the examiner thinks the candidate is going to run off after the test and fly a piston twin with no autopilot and nothing but a raw data needle - then that is the standard they (well, I) would want to see - but both are valid and legal.