There was a precedent in 2010, where the government instructed its political staffers not to appear in front of a committee. I believe it was this committee. The argument made then was similar to the argument being made now, namely, that this was a matter of responsible government and that the ministers were the more appropriate witnesses to respond to questions from the committee. In that instance, in 2010, there was no order of the House. It was an order of the committee, but the claim made and the grounds given were the same.
On April 12th, 2021. See this statement in context.