That is quite true.
But in some sense... Isn't that kind of a bit of spin? Final Fantasy XV: A Realm Reborn by Hajime Tabata didn't begin production until 2011...
...But Nomura and co obviously had a task for 2006-2011. They made all kinds of content. I think SE expected that project to eventually come to fruition but it just wasn't happening, so they pulled out the brakes (and the producer).
I really don't know if the Nomura failed production thing is entirely true. I'm not saying that it isn't a possibilty.
But look at his track record:

Nomura way pretty loaded from 2006-2011. He directed 4 games in that timeframe and Kingdom Hearts Dream Drop Distance released in 2012.
Tabata became a co-director in late 2012.
I'm not saying your conclusion is wrong but I think there is maybe more to it.