I've come across papers in which an author cites an unpublished manuscript by listing the author's name followed by "ms" enclosed in parentheses. So, for example:
As Surname (ms) points out, this view faces a dilemma.
Surname, N. (ms). "Title." Unpublished manuscript, December 15, 2015.
I've seen this in papers that otherwise conform to the APA style guide. However, this specific convention doesn't conform to the APA style guide, which recommends enclosing the date that the work was completed in parentheses or, if the date is unavailable, enclosing "n.d." in parentheses:
As Surname (2015) points out, this view faces a dilemma.
As Surname (n.d.) points out, this view faces a dilemma.
So my question is: which style guides, if any, recommend using "ms" in this way? And what is the APA's rationale behind including a date when the work is unpublished? Isn't there a risk that it could mislead the reader into thinking that the work has been published?