SMB protocol support for file based vCenter backup comes with vCenter 6.7 U2 package. It is good to hear that!
Because of scheduling/creating a backup job was not easy in older versions, you have to be carefull for wording, typo. So it was so sensitive while typing protocol line in backup job schedule wizard.
Now it is easy. I created a job easily and tested in my environment, you can see the following Picture. But before look it, please take a look two consideration points:
Typing of location
User name: directly type only username who has right permission on the folder. İf you add domain name it is not running.
Wrong examples: firstname.lastname@example.org or company\tolga
Details of this issue is described in the following blog link.
Output of the job: