Well no, the zero dupe does use HTTP 1.1 301 headers :
http://www.bulldogboard.eu/ducplicate-t5596.html :
So these 302 must come from elsewhere. You should investigate a bit to find out where because it's potentially a problem for SEO. It's no big deal if these are for example url to private forums and topics (a 302 is then used to redirect to login, which is an appropriate use), but it could be a big pain if it was for example from a redirection from an old domain name or things like that.
About the overall raise in stats, if you just migrated to the rewritten url it's normal, for few days, bots crawl like crazy when this occurs, just like if they needed to be really sure about the new locations, and then, it usually goes back to normal crawl rate few days after.
If so, only this could explain most of the increase in stats, even though of course, that's what you get while doing some SEO more visitors, but it's a bit longer run than few days after a migration.
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