I doubt casinos take the time to lower the chances of a gambler winning based on their location, sometimes we hear about casinos restricting some users because they are professional gamblers or sometimes even bans are issued as the gamblers are trying to abuse the bonuses given by casinos, but I have never heard of a casino giving worst odds or lower payouts for the same bet based on their country of residence, and if this was ever found out to be true a backlash would ensue so I doubt it will ever happen.
I also don't believe the casino will make a difference in winning odds based on location or country, all winning odds will be the same for all gamblers regardless of location, so that statement is just a person's assumption because he often loses in gambling and not a fact of actual gambling, all platforms the casino targets more users from all countries that are not prohibited under the regulations of each country.
Myself too doesn't believe in it, but there are differences in Winning when you play on different time zones. I came across similar incident and tried to cross check and found it to be winning when we play on the Western time zone and loss when I was on the Asian time zone. This is just a coincidence, which I later understood when I took the overall profit and loss between the two time zones.