Spam/Type2 folder has no files

The SmarterMail documentation says Spam/Type2 is for a Random collection of messages caught by the existing Bayesian Filter.

I've never seen anything written to the Spam/Type2 folder. I've given "Everyone" permission to write to it. Anyone know what the reason for this can be?

Further to this I've found that marking messages with Mark, Spam does not consistently write the file to the Spam\Type1 folder - it does it only occasionally.