I cannot talk about the commitment you mentioned, but what I can say is that at the inception of the GST, there was a policy decision made that the GST would apply to what is called the “consideration for the supply”, that being the the price being paid. In terms of taxes, there would be only three exceptions: the general provincial sales taxes, the land transfer taxes, and taxes imposed in lieu of provincial sales taxes where provincial sales taxes don't apply.
That was the policy adopted at the inception of the GST. That's why there are many situations where the GST is being applied, even if a component of that price includes a provincial fee, a provincial markup, a provincial tax, a provincial levy.