according to the winstone help the --debug flag takes an integer to specify the debug level.
However the code for the option signifiies this is actually a boolean option.
And if you try and use the option, it is later treated as an integer.
This obviously doesn't work, and as such you can not use this flag to configure the winstone default logging level.
As the Level also is re-initialized by the code it is unlikely that configuration via a JUL config file and system properties will work as expected either.