As I understand it, the fine is optional and is less likely to be levied on people who approach them before being discovered by them. They want the money more than they want to penalise people who want to pay it.
The risks of being caught lying would probably depend on..
.. whether or not the agency in question is paying its taxes. If no other staff are doing so, the owners probably aren't either and you may well further reduce your chance of being fined by pointing this out.
.. whether there are any reviews that are identifiably 'you' dating back prior to any claimed date, or if your agency blurb similarly gives the game away.
If you started working with a new agency or with a new working name, this would remove any doubts in those areas, but if you're happy with your current ones, you may not wish to do that.