From the point of view of an industry observer, it lays Microsoft's often-rumored product fiefdoms bare: Windows RT is a Windows OS initiative. The division responsible for Microsoft Office was either not consulted on this or — more likely — insufficiently supportive.
"Yes," they might have said, "We understand that this is a bet-the-company's-future initiative, tremendously essential to the Windows team. However, we will not support the completely new, modern APIs that you are putting forward. We define legacy, and we demand that our legacy is supported."
So untold person-years of effort go into porting Windows 7 APIs to the ARM architecture, bloating the operating system, destroying its conceptual continuity, and confusing the picture for external developers the Windows team is trying to evangelize.