When the user tells an IMAP client to open a folder, it basically has three options:
(1) show no content
(2) download headers and populate folder with the recevied data
(3) use cached data to populate folder
Now you have made it abundently clear that you don't want option (3), you seem to be somewhat opposed to option (2) so that leaves option (1).
A valid choice, though I am not sure how many others would use a term like "smarter" to describe such behavior.
KMail (with or without Akonadi) uses option (3), based on the assumption that its target users prefer folders to be populated automatically upon open and prefer not to download headers every single time.