Whether any particular firearm is classified as prohibited or not, is up to the judge, at your trial.
Do you think your judge is going to agree that your firearm is not prohibited because
the FRT:
1) isn't law
2) isn't publicly accessible
3) is not updated or announced to licens holders.
Or are you going to have some evidence that relates to your particular firearm that proves it isn't captured under any provision of law that could be interpreted as meaning your firearm falls within the prohibited class.
You are correct that the FRT isn't law. Its just the RCMPs opinion. Murray Smith himself testified that people are free to form their own opinions and live accordingly. To each their own.
I hope it works out for you.