Yes, this is expected. These tags are all considered "unsafe"
to copy by default since they may change they way an image is
rendered. And since the YCbCrPositioning tag is mandatory by
the specification, ExifTool uses a default value for this tag
since it wasn't copied from the image. In the
Name documentation, unsafe tags have an exclamation
point after the format name in the Writable column.
Unsafe tags must be specified explicitly if you want to copy them
from the source image. ie)