I would expect a rewire carried out in 1971 has had a number of additions and modifications since the initial install 50+ years agoTo suggest a rewire you must support it with evidence. My house was wired in 1971 and it is perfectly sound.
Back then the 3036 Wylex board was still the consumer unit of choice and ELCB's were generally only found on TT systems, the 14th edition regs were a lot less onerous and having moved on 4 editions and many amendments and the proliferation of appliances needing power over the last 5 decades and having also become a more litigious society it has certainly changed the landscape of how older installations are viewed
I'm sure that if you were carrying out an EICR on an untouched 1971 rewire you would not be giving it a perfectly sound assessment with no C2 or C3 codes