Hi,
I'm taking the liberty of dig up this topic as it's still relevant.
Although the "refine seamlines" function works quite well, there are many situations where Metashape prefers to cut images over buildings rather than go around them.
Particularly when there are complex textures like trees (foliage) next to the buildings, which Metashape prefers to bypass.
We then have to spend a lot of time checking and modifying the mosaicking or use third-party software that allows the import of buildings shapes.
In many countries, building shapes are available for free.
Best Regards
Maxime