I think he is saying that sound is only the medium not the music itself. Therefore perfection of sound is not essential for listening to the music. As an analogy, were we bibliophiles and not audiophiles, it is unlikely that we would be arguing that War and Peace would be a better novel if it were printed on whiter paper with more dense back ink. A bibliophile may collect rare editions but I don’t think any would claim that the work itself was changed in some way. NB: I am ignoring textual revisions to make my point as that is something else entirely.
As for driving I think that is probably more to do with the creating a psychological condition for intense listening where the body is occupied with a task that is done more or less automatically . Rather like many ( all?) orders of Christian monks who see work as a form of prayer. BTW, I just remembered Zimmermann was referring to driving at night with little other road traffic.
I have encountered a comparable situation when commuting to work in an old car with a crude radio installed. A single speaker in each front door and no crossover. Yet I could be really hooked on the music to the extent that I would drive around the block until it finished. Then buy the record but never be able to recreate that intensity of experience irrespective of the refinement of my home audio system.
I agree with you. As I am currently responding to questions/points in this thread it is difficult to start a new one unless I have a substantive issue to raise. However maybe the next contribution with an original point could start a dedicated thread?