From what I read above it shows that they have requested for mod to lock their previous thread which I think is not right to lock the already existing threads and focus here. But even if they must lock that previous thread it's always advisable to go make official announcements then Link this new thread from the old thread for people to know what is happening to their announcement thread.
There is nothing wrong with having new ANN thread and asking mod to lock the older thread or lock by themselves, something normal here unless it is done many times.
Announce the new thread on the old thread before it is locked is better but not a must because sooner or later the new one or the active one will be the one noticed by most members here especially if the new thread is having good activities from themselves and from other members.
Even if there are some players who know about this casino from the old thread and they want to ask something, they will find this new thread as well later once they noticed that the old thread is locked already.
It may seems usual to you but flashing to back a casino their profile was locked due to not following instructions after which they learnt their lesson and their campaign was managed by reputed campaign manager, it was on a case that he intervened on them before their profile was released and they resumed posting again. It wouldn't say anything about this casino as I know less about them, but still if things are not properly placed there is every needs and necessity it's being placed fine to avoid any penalties.