Websites also use other means to gather data about you or your device through things like cookies. So they can probably predict where you are accessing the service from. I also noticed some sites that can easily detect that you are using a VPN or Tor browser.
Then there is also KYC can be requested at any time. Personally, I don't like getting in trouble. It's best to avoid use of VPN usage if it's prohibited as per the terms of service.
It's very easy for any website to detect whether website is using a VPN or Tor if they really want to detect. There are only a few websites that care about that, most of them don't have to worry about that but when it comes to VPNs, it's not always easy to detect. You can buy a brand new IP and connect to that dedicated IP. In that case, company won't be able to detect that you are using a VPN because that IP belongs to you and no one else. Normally, they detect VPNs because lots of users share the same IP, they also have list of IPs that belong to VPNs because there are companies that work on collecting them.
My personal opinion is that with dedicated IP, it's easier to risk but if someone is from restricted country, then they should keep in mind that they shouldn't deposit more than they are willing to lose and if they also win big, they'll have to forget about that.