Some of the copy didn't appear in the tier language, or is confusing -- ignore the language in the tiers, this is definitive:
SIGHTSEER is eligible for digital stretch goal rewards only: extra wallpapers, digital media, downloads, etc. that may be unlocked in the stretch goals.
ALL TIERS ABOVE SIGHTSEER are eligible for digital stretch rewards AND physical ones as well: additional pins, additional prints, and other items that might be unlocked in the stretch goals.
Sorry for the confusion!