It has been long been the case that Google indexes some 302 redirect URLs.
Years ago you this was used by black hats for "hijacking" listings. They could create a link that 302 redirected to another page and Google would sometimes put their redirect URL into the SERPs in place of the legitimate page. The black hat would then change the redirect (or even cloak it) and steal organic traffic coming from the Google search results.
Google changed their algorithms to favor the actual page 99% of the time instead of the redirect. Now 302 hijacking no longer works. Matt Cutts discussed this on his blog. He gives an example of why Google might want to occasionally index the redirect rather than the destination page:
Let’s take an example from the tiny fraction of the time that we may reserve the right to show the source page for a 302 off-domain redirect. If you run wget on
www.sfgiants.com, you’ll get a 302 redirect to a different domain, and the url that you’ll get is pretty ugly:
http://sanfrancisco.giants.mlb.com/NASApp/mlb/index.jsp?c_id=sf. Please set aside that you are probably a site owner or webmaster for a second, and try to step into the shoes of a regular user on the street. If we had a taste test, how many users would prefer to click on
sfgiants.com and how many would prefer to click on
sanfrancisco.giants.mlb.com/NASApp/mlb/index.jsp?c_id=sf? Normal users usually like short, clean urls. They are less likely to say “
mlb.com? I wonder what that stands for? Hmm. Maybe major league baseball? Is that the officially licensed name, I wonder? It probably is. Yes, it looks like
sanfrancisco.giants.mlb.com/NASApp/mlb/index.jsp?c_id=sf is the correct url from my query.”
So if you have a URL that redirects, Google may choose to index it. They may choose to do so especially if the destination URL is not crawlable. For this to happen, Google has to be able to crawl the URL.
For redirect URLs listed in robots.txt it is another case completely. Google may choose to index a URL that is listed in robots.txt even when it can't crawl it if it feels that the inbound links to it are important enough. In such cases it uses the anchor text of links in the SERPs and does not crawl the URL at all. Google has no knowledge that the URL redirects. This is the case for the three real world examples that you give. If I search for the destination pages by name, I can find the destination pages on the normal site.
Most of the time these URLs blocked in robots.txt will only appear for
site: searches. (I'm pretty sure I've seen Google's John Mueller say so, but I can't find the reference now.)
So if you don't want your affiliate links to show up in the search results, it appears than neither 302 redirects nor robots.txt is a foolproof solution. I would recommend that every affiliate link on your site has the
rel=nofollow attribute on it. Then Google will be much less likely give the URLs enough link juice that it might think they are worth indexing.