I agree that use of Realm Works is best if you have the book or .pdf to read ahead of time. However, once I've done my read through I shouldn't have to pick that book/.pdf up again as every last bit of info I need to run the adventure should be in Realm Works. Is this not in line with how Paizo thinks I should use their products?
Everything you need to run the adventure is in the Realm... other than Players, GM, dice, rules set, and imagination.

The overland map mentioned is not needed because this mini-adventure doesn't make use of overland travel or random encounters, unless the GM decides to add them. Remember, it is a free adventure for use in demonstration games to let new players try the game out... it is intended from the beginning to follow the KISS philosophy (Keep It Simple, Stupid).
IF a GM wants to include the adventure as part of a larger campaign.. such as the Jade Regent Adventure Path... then the GM is free to do so, and mention is made of where in the world of Golarion the adventure takes place. But that's not necessary to run the adventure at all.
It is unfortunate that the overland map is referred to at all.. but the Realm is just faithfully reproducing the text of the module, and it is not there, either. An argument could be made that a GM note should be attached to that snippet.. something like... "The original printed adventure mentions a map, but there is no such map. The trip should just be described without reference to a map."