Jeppesen in paper format has two charts on a page, one on either side.
If other side gets changed, page get renewed, with one side possibly without changes.
Updating the date on this page ensures the page is correctly updated each time even if procedure on reverse is the updated source of information.
It does appear to especially electronic chart users that the logic seems awkward or flawed, but there is reason for the reported madness.
Old school pilots may remember updating their own chart sets regularly, they will remember this...