You will get surface rust on any springs where the coating get's damaged or is too thin. It is fine. Springs (even cheap ones) are very durable and by the time any rust on them develops to a point where it is a problem the rest of the car has probably turned into a pile of scrap anyway.

They are probably good for a few more decades.

I'd re-read the posts so far, that's 100% by design... Andrew from RCE's explanation is very clear.

Yeah I saw, more just in disbelief; it looks counter intuitive but I get why it works