Log bug?

I am new so prone to newbie mistakes, while looking through logging I cam e across what looks like a bug in the log:set area. As you can see by the events below the help says to use DEFAULT as the unset level but it errors out.

openhab> help log:set
DESCRIPTION
        log:set
    Sets the log level.
SYNTAX
        log:set level [logger]
ARGUMENTS
        level
                The log level to set (TRACE, DEBUG, INFO, WARN, ERROR) or DEFAULT to unset
        logger
                Logger name or ROOT (default)
openhab> log:set DEFAULT
Error executing command: Can not unset the ROOT logger
openhab>

so bug that I should report or newbie issue?

As it says, you cannot unset the ROOT logger.

Try:

log:set DEFAULT <bindingpackage>

As I was not aware of what the root log level was prior to me setting it to DEBUG the help information suggests I can unset back to DEFAULT as a valid log level.
The error as you say, states I cannot use it with root, so what should I set root back to make it as out-of-the-box, before I changed it?

The default level for the root logger is WARN. You can see this in the base logback.xml file.

Thanks!