My company runs status match validation technology & intelligence for airlines.
Here is what I will share:
1) Validating your Velocity status is simple. Many methods to achieve this.
2) Our co runs a 'global loyalty match' list, which effectively is a database is people who have status matched from where, and when.
3) Customer lifetime value is a metric Qantas and other airlines use to determine your future value. Many factors play into this score. Qantas may buy data from third parties to build a profile on you -even if you've never flown with Qantas. Think Taylor Fry.
4) Qantas has some ability to know when you fly with Virgin even if you never tell them.
Loyalty isn't just some fluffy marketing program to make you feel good. It's straight-up data warfare, and you're the product.