I agree with your observation, this is online we are dealing with developers, who should be transparent on what they are giving out, they claim they are giving millions, it should be verified by an independent body, not testimonials coming from random people, I don't see in the homepage that they are verified, licensed and regulated or even popular media coverage.
People should do their research we are not talking of hundreds of dollars here, they are claiming to give out millions here but no transparency on their part, you have to check the legitimacy of what they are offering before being tempted to deposit and bet.
If those winnings wont be directly be cashed in into users account or simply needs to have some confirmation first or process initially came from them then you cant really be that too confident.
Dont know if those winners in the past are valid ones or just simply some show off just to make look the site is working as it should be but i do still have those doubts.