For most major historical buildings there'll have been some efforts made in the past to capture the detail of the building, as accurately as possible, based on the best technology available at the time. This means that it's vanishingly unlikely that the most detailed model of any major landmark will be from a video game (for anything that's world famous that requires constant maintenance, those chances reduce to zero).
Ubisoft's achievement in creating a perceptually accurate, highly detailed 3D model and making it available to millions of people as part of a mass-market product shouldn't be downplayed. It is the leading expression of architectural beauty in any video game (I guess arguably, but...only barely arguably) as well as a spectacular technical achievement. It is also totally plausible that the restoration work will double/triple/quadruple check details using a variety of sources and that AC: Unity (or, more specifically, the material used during Unity's creation) might be one of those sources. It also shouldn't be up-played though - when it comes to accurate modelling of large, historically significant real-world objects, video games won't generally be at the pinnacle (or very near it).
