This article was wrong and Google told us Keyword Planner data does indeed use organic search data, like Bing does.
Here is an update from Google's John Mueller:
The AdWords Keyword Planner folks pinged me about their data: it includes all search data (we'll add to the docs). pic.twitter.com/15dKwOLYSf— John Mueller (@JohnMu) July 8, 2016
There was some confusion about where the Google Keyword Planner tool gets their estimates. Is it based on organic searches or does Google only look when there are ads available for those keywords. The answer is, only for ads - not organic search.
Glenn Gabe responded to Robb about this on Twitter after he asked the question on the Friday Google hangout where John Mueller said he doesn't know about the ad tools. Glenn said he asked several AdWords reps who told him that it was paid search only. Clearly the AdWords reps don't know what they are talking about...
@robbtweets Hey, saw your question in the webmaster hangout. AW Keyword Planner is based on queries where ads show up. Not pure organic.— Glenn Gabe (@glenngabe) July 6, 2016
@robbtweets The only tool that's purely organic search data is via Bing Webmaster Tools. Unfortunately, it's not that great. :)— Glenn Gabe (@glenngabe) July 6, 2016
Good important distinction between the tools if you are unaware of it.
Of course, Search Console can give you your impression data but not forecasts or estimates.
Forum discussion at Twitter.
Update: Supposedly the AdWords rep was wrong and the data is not just from ads, it does come from organic. Hmmm.... Looking into this more.