Maybe that's their process and they don't just disclose that affiliate accounts require an approval. But what matters now that it's fine and your account is approved.
Normally, that's how things work everywhere. I believe those who are used, or familiar with how casino affiliate accounts is operated know that every affiliate account needs approval before it can be functional and that's why it's best to register casino affiliate accounts through the link provided by the casino representative or affiliate manager.
On his end, it's now okay the message is just different though but it's good that the representative has been cooperative with that problem that px has dealt with, no problems anymore and he's good to go.
It will be ideal if these bonuses are stated in clear terms (no hidden conditions) for everyone to decide if its what they want to get involved in.
All casinos have their own ways to promote these bonuses and how these promo are going to be eligible as per participant. That's why when something is cool and you want to join, you all need to do is to check all the details and see if there are hidden rules or none. Typically, the better the promos or rewards, you should expect that they've got quite harder requirements.