Projection query with new fields/properites ignores entries that haven't set those properties yet

Projection query with new fields/properites ignores entries that haven't
set those properties yet

I have an Article type structured like this:
type Article struct {
Title string
Content string `datastore:",noindex"`
}
In an administrative portion of my site, I list all of my Articles. The
only property I need in order to display this list is Title; grabbing the
content of the article seems wasteful. So I use a projection query:
q := datastore.NewQuery("Article").Project("Title")
Everything works as expected so far. Now I decide I'd like to add two
fields to Article so that some articles can be unlisted in the public
article list and/or unviewable when access is attempted. Understanding the
datastore to be schema-less, I think this might be very simple. I add the
two new fields to Article:
type Article struct {
Title string
Content string `datastore:",noindex"`
Unlisted bool
Unviewable bool
}
I also add them to the projection query, since I want to indicate in the
administrative article list when an article is publicly unlisted and/or
unviewable:
q := datastore.NewQuery("Article").Project("Title", "Unlisted", "Unviewable")
Unfortunately, this only returns entries that have explicitly included
Unlisted and Unviewable when Put into the datastore.
My workaround for now is to simply stop using a projection query:
q := datastore.NewQuery("Article")
All entries are returned, and the entries that never set Unlisted or
Unviewable have them set to their zero value as expected. The downside is
that the article content is being passed around needlessly.
In this case, that compromise isn't terrible, but I expect similar
situations to arise in the future, and it could be a big deal not being
able to use projection queries. Projections queries and adding new
properties to datastore entries seem like they're not fitting together
well. I want to make sure I'm not misunderstanding something or missing
the correct way to do things.
It's not clear to me from the documentation that projection queries should
behave this way (ignoring entries that don't have the projected properties
rather than including them with zero values). Is this the intended
behavior?
Are the only options in scenarios like this (adding new fields to structs
/ properties to entries) to either forgo projection queries or run some
kind of "schema migration", Getting all entries and then Puting them back,
so they now have zero-valued properties and can be projected?