for me it's not a type of gambling, but it's a job or job that you know you can not lose, not as a gamble it sometimes hurts you, although there is a bit of bitcoin involved in gambling like casinos , do not just go there because it's a gamble.
How is Bitcoin a job? It is a decentralized digital currency, it is never been a job. I think they are just comparing Bitcoin into gambling since it is risky and investing on it is like gambling.