As far as I know having multiple accounts from one owner is prohibited by every online casino there is because of people taking advantages of their bonuses and promotions.
As long as all rules are respected a person can have as many accounts as he is want. As you said people that have multiple accounts usually take advantage of bonuses and that's when their accounts get blocked and they come here asking why. But as long as you respect all the rules and don't abuse promotions you can use multiple accounts.
I highly doubt this exception to even going by the rules because in every site I know of there is a point in their terms of service where if they find you are accessing multiple accounts from the same ip address they can suspend the accounts in question and even the winnings they have.
You can register for more than one account sure but once you win something and request a payout your account will be investigated and they will refer to the point in their terms of service and have the right to ban the accounts in question.
I fully agree that multi-accounting with the reason to abuse bonuses should be prohibited. First of all, I have one single account, so it does not apply on me. I am waiting on their answer to find out how my account is connected to the other. Second, to be honest I did not even check if Cloudbet has any kind of promotion, like a first deposit bonus, money back, or something like that. I am a seasoned punter, I don't care about deposit bonuses and always reject them mostly to avoid any rollover requirement or withdrawals miseries. Look, my average stake on Cloudbet was around 0.25-0.30 BTC, why should I chase any bonus when I use these kind of stakes? Honestly...