This is quite wasteful, buy may require a core interface change to correct. Currently, the ReplayRendererSelector is checking the DateMismatchSelector, at render time, to enforce the "redirect browser to actual date" so the location bar reflects the correct date. At this point - render time - wayback has already located the file, and downloaded at least the header for the record. This means wayback is:
1) locating and downloading the W/ARC record header
2) determining the date of the record is not what the user asked for
3) redirecting the user to the actual date
4) doing another query, followed by another locating and downloading of the W/ARC record header
5) finally showing the record to the user
#1 is a significant amount of work, and could be short-circuited, by adding a "pre-download" callback to the ReplayRendererSelector interface..