I don't watch those sorts of streams, but they do it during streaming? They change the country-IP in their VPN app and continue playing?

That's laughable because that could become an issue between the provider and the casino itself in the future. Can you post a link of one of those videos?
Of course I'm not advising/recommending others to do it, better to ask support when it comes to this situation but I myself sure that changing IP to bypass provider's restriction is a common thing and some casinos do not take it as something against the terms.
I've asked them about it multiple times on their customer support but they always say using of VPN is prohibited. I once asked if it's ok to use vpn to bypass ISP restriction since my internet is blocking the website from accessing it and they still said I should not do it. They even thought that I was gambling from a restricted country that is why I'm asking them.
Seeing many users in this thread that they use vpn contradicts their customer support's statement. I guess it just depends on the user's consent if he is going to use vpn or not. As long as the user only use 1 country from the VPN and no illegal transactions happens on the account, it won't be flagged by the website as suspicious.