I am pretty sure in the terms its said somewhere "no more than 1 account" most sites have this term even if they don't enforce it.
What is really strange is why create so many alts, and be too lazy to think of nicknames that aren't related to each other.
Most likely this was deliberate. So knows, maybe he has more than 1 PC and is logged in simultaneously so he created all these accounts. One account for his work computer, home computer, mobile, vacation home computer, etc.
Nope, mostly site will never give you more multiple accounts, what I know that the only site that giving 2 account per ip is bitsler but I do not know if they put it on their ToS or not. Anyway I just checked on primedice ToS and here what I found, so I do not think they allow players to have more than 1 accounts. Usually people created many accounts just for abusing the faucet but if the conditions they do not abuse it, I wondered if this is allowed or not
5.1. PERSONAL USE. The Service is intended solely for the Users personal use. The User is only allowed to wager for his/her personal entertainment and may not create multiple accounts, including for the purpose of collusion and/or abuse of service