The UVUnwrapper class passes the position etc attribute arrays into the xatlasjs addMesh function directly - however, if the geometry uses interleaved attributes then this array contains data for every attribute and will subsequently produce incorrect UVs. Likewise, even if a BufferAttribute is not interleaved it may still use arrays with smaller bit depth (eg 16 bit normals) which will be passed into xatlas, which looks like it requires Float32 buffers unless I'm misunderstanding.

It would be possible to unpack the buffers before generating so they can be used but throwing an error so the user knows the generated geometry is invalid would work, as well.