Exactly. And you could likely use standard grade caps and still have a drastic improvement. 40 years ago there were no "audio grade" capacitors. My perspective is, you don't know what abuse your unit has been through unless your the original owner. Most of these components are ticking time bombs. Its like buying a 40 year old car with 100k miles on it and a fresh paint job, and expecting to drive it across country.
I agree. 40 years ago there was no computer grade capacitors in common use. Digital is very fussy about parts and capacitors had to step up to the spec.
Then computer controlled mass production made manufacturing and quality control much better. Caps today are light years ahead of the 70s tech and manufacture.
I'm not convinced about the whole "ticking time bomb" thing.
They are not that hazardous by a long shot.
I've never seen a unit blow up due to old caps and I have found many caps that were bad. It has always been a situation where the bad cap is causing noise, some a little noise, some a lot of scary noise!