The reference to S.I. 605/22 - Planning and Development (Exempted Development) (No.4) Regulations 2022 in the Department’s Briefing Note referred to in the details of your question was an informational point contained in the 'Context and Overview of Current Accommodation Pressures' category of the Briefing.
This information provided context on the the efforts that the Department has made to try to secure additional accommodation in a wide array of repurposed buildings.
It was not outlined as an informational point that an exemption would be sought for the use of Ryevale House.
I trust this clarifies the matter.