Unfortunately Apple didn’t write MacOS to use the industry-standard methods of server-side SMB copy. The SMB server has to advertise itself (globally) as being a MacOS SMB server and supporting their specific IO/FSCTLs.
The problem is that enabling with vfs_fruit and fruit:copyfile=yes as documented in thread may also cause unwanted behavior:
WARNING: the copyfile request is blocking the client while the server does the copy.
In this case, “client” is the smbd client process on the server.
It’s being looked at, but this is more complicated than just “flip the switch and magically works.”