The phrase "potentially shippable" has little to do with shippability.
Here is the definition from Ken:potentially shippable means that /the
increment consists of thoroughly tested, well-structured, and
well-written code that has been documented and built into an executable
reviewable by the Stakeholders/ [Ken Schwaber, /The Enterprise and
Scrum/, Microsoft Press, 2007, pg. 112, paraphrased].
As you can see, it has nothing to do with amount of functionality; it has everything to with technical quality.
Not many people agree with this in my company at least but i would really like to push on this if i would been a product owner for any release or a product in future.