I don't know how far your casino platform is, but it should never be limited to these few countries. You need to expand to more countries and allow gambling (in countries where casinos are legal), then the casino platform will attract more gamblers. Because I think gamblers exist in all countries of the world (secretly or openly), but I think the more countries you allow, the more popular the casino platform will be for gambling and betting.
You clearly didn't read his post properly. He mentioned restricted countries implying that the site isn't accessible in only those countries and is accessible everywhere else. Reread what he stated.
It is best for casinos to clearly state their stand on the regional restrictions so that visitors can see for themselves before registering so that they do not blame anybody it they go against the ToS.
Valid reasoning. Logically, gamblers wouldn't be able to access the site if their country was restricted, but such lists are essential for clearing up any confusion completely.