PRIA only requires 5 years to be legal.
There is no law which compels a company to request your employment history beyond 5 years, but there is no law which prohibits it. It's perfectly legal for the company to request your full employment history, many airlines do. The fact that PRIA only asks for 5, doesn't give you a reason to only provide 5 years.
You have 3 choices:
1) Give you complete employment history.
2) Only give 5 years and most likely be disqualified because you didn't provide the requested information.
3) Don't apply.