Yes, it looks like a full log when set to Debug (not translated).
So after I did this, I set it back to Normal (translated) and ran it again – empty log file again. I tried viewing the log while the job was running, and it looked like nothing was writing to it.
Then I set the logging to Normal (not translated) and backed up again. That gave the same result as Normal (translated) – [INFO] header lines only, no log content.
I thought I might as well round out the experiment by running it with a Debug (translated) log. This produced a log that looked a lot like the Debug (not translated) log, so I switched the setting back to Debug (not translated) in case I had chosen the wrong debug setting the first time, and ran it one last time. This produced the same log I got the first time, so I guess there is no difference between Debug (translated) and Debug (not translated)?
Don’t know whether this helps, but we reviewed emailed log files and determined that the last normal log was on 9/27/17. On the next backup, 10/4/17, we saw the first empty log. I note that there was an update from vs. 3.4.1 to 3.4.2 during that interval.