In CANVAS theme, and all other themes using Canvas as a PARENT, the layout for 'default' is wrong.
If you look at BASE theme it gives the 'default' layout as:
However, if you compare this with CANVAS theme you can see the difference:
In BASE there are NO regions or default regions declared, whereas in CANVAS there are.
It is hard to understand why this has come about, as the default layout in BASE states clearly:
So it looks very much like this has been an oversight from the very beginning of Moodle 2.0 themes!
I am just wondering if it is this change of layout in Canvas that has been bugging Moodle all this time without detection, causing problems where problems should not arise? Making pages works differently for no apparent reason? One problem comes to mind when all blocks are docked, so that by default in BASE it would be no blocks, yet in Canvas, Moodle would still be looking for block regions, and may even be giving out wrong variables and confusing Moodle? Scary!