This is from Mark Chirnside's article below. Looks like that change took place during the 1928 refit.
"This is a clear reference to the new B-deck suites. It noted that some of the suite rooms were twenty-two feet long, and that every single one was ‘equipped with a private bathroom and roomy wardrobes.’ The report also clarified when the first class dining saloon’s forward bulkhead was moved forward three frames (nine feet). It noted that the dining saloon had been extended and a dance floor fitted between December 22nd1928 and Olympic’s February 13th1929 Southampton departure. The report confirms that the extension of the first class dining saloon and the installation of the new B-deck suites (as well as some of the new private baths) took place during therefit at the turn of 1928-29.The redecoration of the Café Parisian, other minor changes to first class, the new tourist class public rooms, construction of new third class rooms forward on D-deck."