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
Please do not compare both Casinos (Primedice <-> Bitsler). They differ in so much from both professional sides.
For instance in Primedice you are allowed to have multiple accounts and play with them as long you follow the rules such as Faucet ones:

Where in Bitsler admin is so locked into bots / multiple accounts that you might be scared off in having such multiple ones.
If you didn't knew, Bitsler was DaDice before, same Staff just different Domain. They blow up their DaDice due to possible faucet levels farming and tried to block everyone's withdrawls and eventually busted in so they had to change their Domain / return back after some time like it was a new Casino / staff team (Bitsler)
I am not really sure if you are following from what I said here. I told you bitsler allowed 2 account because that is what I know from playing there a lot, so updates will known. But I seldom played on primedice, only when there is a big event so I do not really know about their terms or anything. But when I checked on their ToS, it does not said that they allowed player to have more than 1 account like most of dice site