well I understand your points. I believed referral bonus is given to someone when the customer refer the site link to a friend. And I have been receiving such email from casinos but I ignore them. While welcome bonus is the one we get when registering to a new casino site but I registered to a casino recently which promised me to to give welcome bonus but I didn't see anything. That is not withstanding. Many gamblers join some casinos because of the bonus while some abuse these bonuses. Though some use it to win big, that is their luck.
You are very correct but then not just a refers bonus given to a gambler when someone register through the link, but also it goes further to as how much wager does the gambler downline have and what becomes of them at the end of the month and in total it is paid out to the gamblers monthly, so that becomes both referral and affiliate.
So much so the bonus is or subject to wager requirements like the welcome bonuses where you have to wager it at the end of the day which will increase your own risk.