Absolutely.
Mr. Poilievre was quite right at the time, but that might be less true today.
As I recall, at the time, when my hair was a little less grey, he defended the fact that the Prime Minister wasn't invited to committee meetings, as you pointed out, and he said it was not up for debate.
As you so eloquently put it, he went on to say that ministers are accountable to Parliament, to committees and ultimately to Canadians.