Yes, the files are written by MacOS... no matter how your Mac touches a folder, whether directly attached storage or via shared SBM or CIFS, it will write them.
A tip to those who care about such things.
Mavericks introduced support for SMB 2 protocol but it is written by Apple and it is buggy. It will give lots of problems. To force SMB1 you must use CIFS:// when mounting remote shares via SMB. CIFS will use the older driver which is much cleaner.
Thanks. The only reason I asked is I was thinking that maybe these files could cause problems when working on a Mac in Windows. Just a thought but you have found something with the SMD protocol.