When I run the script in Script Editor, and have the Console app running - it does appear in the Console.
The logger messages above are:
SpamSieve [Apple Mail Rescue Good Messages] Finished checking mailbox “HIDINGEMAIL” / “Spam”:
SpamSieve [Apple Mail Rescue Good Messages] Messages to process in mailbox “HIDINGEMAIL” / “Spam”: 0
And a bunch of similar messages to the above (obviously I hid the email with HIDINGEMAIL).
However, when I “Apply Rules” manually (or wait for it to automatically happen), then nothing happens. (nothing in the console.)