This is some strange usage of the words 'On Record' (by Kuhn) that I wasn't previously aware of? Whether or not you agree with his analysis of the Qt/Gtk answer as containing hidden hints that, if you read between the the lines, reveal that Canonical may be seeking an Open Core model, it certainly isn't Canonical going on record that they are.
By the end of TFA, Kuhn's asserting things like that in the Qt/Gtk answer Shuttleworth "explains at great length how lucrative and important Open Core is". Which, if you actually read the transcript, is just nonsense.
Personally, I don't see that Kuhn's analysis of the answer is correct anyway. It seems pretty clear to me that the reference to Trolltech having had "many options including proprietary licensing" is referring to them selling licenses for Qt to companies that wanted to make proprietary software with it and so that couldn't use the GPL'd version, back when it was GPL and not LGPL. That isn't an Open Core model, it's just dual-licensing (i.e. all of the software that is sold under a proprietary licence is also available under the GPL -- as opposed to the software available under an open license being a subset (the 'core') of that available under a proprietary license; which is the Open Core model as I understand it).