It might actually be impossible to get agreement, so “consultation”.... This is the sort of power that it's very hard to imagine being abused. I can't think of how one would abuse this particular power, and hence “consultation” seems to be reasonable.
Otherwise, effectively, not only do individual House leaders have a veto over the new time, but it might be that they are simply unavailable, and hence you literally can't bring Parliament back without violating the Standing Orders, and that would be a meaningful issue.