Is it true that that the probationary period for B class licences is five years?

No,when you first obtain a driver's licence you begin a two-year probationary period. If your licence is revoked during this period, you will have to pass both driving tests (theory and practical) once again before a new licence can be issued. This probationary period does not apply for AM (moped) class licences.

You are not judged differently during the probationary period, but if you are found guilty of a traffic violation that leads to your licence being revoked during this period, you lose it altogether.