This amendment indicates that really no member designated as the chair can hold the position for more than 30 days. Bill C-59 allows a member to hold the role of chair for 90 days. That's far too long, and a vice-chair should be in place to cover off all the absences of a chair in the first place, so that's the rationale behind this particular amendment.
On April 17th, 2018. See this statement in context.