The prep work is very important when doing plating, and Schwinn generally did pretty good prep work, followed by the traditional heavy-metal plating process. So when you get rust, at least when the rust is getting start, you get spot rust. The rust that is lethal is the type that gets under the plating and then runs along the base metal, forming "bubbles" in the chrome. The chrome then flakes off. This can eventually happen even with good chrome if the part is neglected long enough, but it certainly takes longer and take more neglect than with cheap prep and plating. If you want good chrome, you need to have good, clean prep and then a willingness to go through the plating (triple plating) steps rather than cut corners.
I tell people that when you're looking at a plated part, you're not so much looking at just the brown on the surface to assess condition (you are to a degree, I guess, but it's not everything), what you're looking for is lines or bubbles under sections of plating, that would indicate the rust is running under the plating and is on the base metal. You see that kind of insidious (and often very destructive) rust on cheaper parts many times, but you can get it even on good stuff that is neglected enough.