TheMadScientist - 5:51 am on Nov 7, 2012 (gmt 0) [edited by: TheMadScientist at 6:16 am (utc) on Nov 7, 2012]
Your hypothetical situation doesn't make any more sense than lucy24's comment about confusing bots, and the noarchive tag used to behave as you described, but I removed it from all my sites after running it for years, because it was treated like the nosnippet in some cases. Why? I really don't have a clue, but in some cases it was ... It could have just been a glitch, but I haven't ever used nosnippet yet I had no preview for some key pages, so I pulled the noarchive and 24 hours later the preview was back ... Go figure.
I don't feel like arguing or even giving answers any more ... If you and others want to believe canonicalization has something to do with the issue described, even though it defies logic, reason, and server settings/bot interaction, then go ahead...
I Will Add: I assure you, I didn't pull the noarchive tag off of 50,000+ pages lightly ... It was the only tag I ran on all pages across all sites and it was there for years without issue ... I thought for quite a while before I pulled it.
[edited by: TheMadScientist at 6:16 am (utc) on Nov 7, 2012]