If they have samples, I'd expect them to want to distribute those (hell, every time I see a graphene related company I look on how I could buy a sample), but I'm not even sure about what I'll get after contacting them. Is the contact there for investors only? For hiring?

If they want people to start using their graphene for something, they may need to add a "get a sample" button somewhere. They may not be vaporware (there are enough labs producing some kind of graphene out there, there are even sites that are more clear on what they produce and yet aren't clear enough on how to get some), but there isn't a line of people wanting to jump over any obstacle to get it either.