I once tested the UK system like that by sending an envelope to myself with just house number and postcode. It worked perfectly, yet convention remains to laboriously write redundant information every time.

Recipient name, Street address + number, Postcode doesn't sound that laborously redundant, unless your conventions have something more. Gives a larger area where the mail should go, a precise area where your mail should go (that you can compare to the larger area for mismatches) and who should be able to open the mail.

the redundancy improves reliability. Ink runs, mail gets wet, some small degree ambiguity will likely always exist, etc

Well bully for you. For those of us who live in flats it's not so simple. If you were to put e.g. flat 8 and my postcode there are about 4 or 5 choices so you're probably not going to get your mail.