FNB need salary to be credited for Forex limit increase

FNB recently reduced international transaction (Forex Limit) monthly limit to 15k for foreign nationals working in SA as per exchange control regulation as per their representative . It can only be removed if your salary is credited to your FNB account. I emailed FNB and called them however there no satisfactory answer was given. When FNB opens any account they ask for income source which helps them to estimate spending capacity . This raises following questions:

1) If there is no Salary getting credited to FNB accounts, on what basis FNB is allocating monthly limit to 15k? 2) If person goes abroad or you want to buy something from outside of SA, FNB is saying you should NEVER user FNB card as we cannot increase your limit. As your salary is not getting credited to FNB 3) Is it regulatory's requirement for banks to process international payment only if salary is getting credited to their account? Or they ask ask for documents which helps bank to determine the income and affordability.

I think, as long as bank can see money is transfer from one valid bank account with in SA to FNB, they can always trace back the source if its required. Also, I think SARS provide compliance status to all banks for an individual in SA.

So, why FNB need salary to be credited to FNB account only? There is ambiguity for this ask for salary account.