No need for apologies! The reports so far did not specify when it was decided Kako would remain in the temporary residence. No room for Mako is understandable but leaving Kako out of plans/design is odd unless the family thought she would also marry soon. The Akishino family will use the temporary residence (as staff offices/storage too) after renovation so they will maintain 2 structures anyway.
I can see savings in leaving the Akasaka East residence unconnected. No idea how or when the private rooms were renovated.
Princess Akiko of Mikasa has a residence in Kyoto but that's reasonable since she has work and many activities in the Kansai region.
ETA: NTV says the Akishino temporary residence will be called the "branch office."
ETA2: Yomiuri published later than other media and says building each family member a room would increase the scale of renovation and budget. Before renovation started, the family discussed and agreed Kako and Mako, who was not married yet, would stay at the temporary residence. Renovation started in March 2020 with the family moving into the temporary residence a few weeks earlier.