I don't remember seeing "Polk" directories here in the Boston area but it would seem to me that they would be published the year before, like December 1960 or sooner. What would be the cutoff date for typesetting a new address in that directory in time for printing?
I have just left a message with Polk to see if they can answer that question.
Someone named Chantal Anderson (the same name, not necessarily the same person) as appears in the U of WA records as a Deputy Registrar, wrote an article about this issue and included a page from the directory. The typed info on the bottom I gather was her contribution.
1961 Indianpolis
copyright, 1960, by R.L. Polk
https://archive.org/stream/polksindianapoli1961unse#page/n3/mode/2up
Link to the Chantal Anderson article:
http://blog.seattletimes.nwsource.com/politicsnorthwest/2009/01/23/_cruise_down_516_13th.html
“The Polk Directory from 1961-62 lists “Mrs. Anna Obama” at 516 13th Ave. east.”
There is another article in which someone asks Polk how and when their data was collected. The reply was rather vague...which is understandable. I think they plagiarize their information.
more on the directory:
http://blog.seattlepi.com/thebigblog/2009/01/14/did-baby-barack-obama-live-here/