Being the largest denomination does not mean they shaped all Christianity. In fact Christianity was shaped before the Catholics split, in the middle east and Asia Minor with Rome being a fringe player.
Their later innovations were mostly left unadopted by the other half of the church and also caused a new split resulting in major intra-Christian religious wars. In fact since Catholics are merely a plurality and not a majority most Christians reject, frankly an understatement, the defining characteristic of Catholicism, papal infallibility.
Attribution is required by the (A)GPL and is standard in forks. What is not required is preserving branding and logos.
For a good reason, those are often trademarks. Had they included them Only office would sue them for trademark violations.
It's a dishonest attempt to override the FOSS license.