If you asking from the guy who are provided you the service.
Off course, they're gonna say that, because is a business scheme (You never say anything bad about your product). But, If you ask from regular person they're gonna tell you different things.
If there has some machine that can make us (Regular) person, verify the RTP and others thing is same. We will believe that, just like "Probably fair" for hash game while we can verify the result by our own check.
That is a bit of a sceptic approach and I wouldn't blame you. In this case demo and real are different because demo is fake money, so that alone should be a good reason not to see them the same because nobody would gamble with fake money just as the same when they are gambling with real money.
This is why I really hope that you do not end up with any misunderstanding but if demo and real are said to be the same, I would assume it could actually be the same. Why would there be difference anyway? It's gambling, you should be aware that you are going to end up losing money, that shouldn't be a secret to you, nobody should think that there is "maybe" a chance that they could profit in the long run.