They track a lot more than just your IP address. They could have information such as your Device ID, operating system you are using, Timezone, Browser type and version and many other things. Check out their privacy policy.
Since they partner with the gaming providers, they definitely either share this information with them or the game provider also has direct access to the information once you try to access their games.
So if you get limited from casino by a certain provider. Just look for casinos that use a different provider or else they will keep getting your accounts in other platforms that use the same provider.
These information is used for many purposes like their platform database on users which later can be provided to government under legal cases, or to detect suspicious activities of their users for defending their business better, or can use to support their users on account recoverires in hacked cases.
When you use a centralized company and don't aware of these things, you can lose your privacy a lot but they can allow you use VPN or Tor, it depends on each platform. Checking their FAQs and ToS before using will help you knowing of those important terms and avoid problems later.
A casino and its partnered game providers can share something common in their ToS but can have different terms too. A casino can allow you by your nationality and IP address but their game providers can not allow you by their differences in ToS.