How so? The players would need to know what every other squad member was earning, and be aware of all dispensations and allowances. Even then, the player cannot be seen as complicit.
They don’t need to know what every player’s earning but they can access the rules of the salary cap as easily as anyone (they’re here
https://d2cx26qpfwuhvu.cloudfront.net/premier/wp-content/uploads/2016/05/03161651/Salary-Cap-Regulations-2018-19.pdf) so if part of their contract involves ways to circumvent these rules, the player will know.
It has been alleged in the past that players were paid in foreign countries, etc. We can see that this would be an attempt to get round the cap so why wouldn’t a player (plus their agent, lawyer, etc)?