No new source, just thinking logically about various iPad releases and the information has currently been provided through the usual channels.
1. There has been nothing substantial to contradict Gurman's November 11th release date. It's not surprising that third party outlets would be shipping after the official release date, and Gurman has seemed to double down on the 11th on Twitter.
2. There is a history of Apple rolling out iPad releases in this manner. The much sought after iPad mini with Retina Display released in 2013 is a good example. It was announced with the iPad Air in October and said that it would ship in November. On November 12th, Apple issued a press release that it was available for order that day and reviews came out later in the week.
3. We are talking about a product line that hasn't seen significant growth in awhile and an offering in that line for all intents and purposes is nearly $1000 with no subsidies. I can understand if Apple wants to downplay the actual launch.