Let it be known to all that whatever we may have experienced and and may hear with regard to any immigration issue, and  visas (of any kind) is totally based on someone else's specific case. I would say that each and every case differs although, the context may seem to be the same. Thus, my conclusion about coming to US after getting the visa is completely dependent on the Officer at POE. I would say it is purely speculative and much depends on individual luck, as well to some extent. Therefore, I would advise Cybro to invite his parents ASAP and make rational decision rather than discussing the issue (which I would say is good to know about it) since there are endless opinions about the subject matter.

Good Luck in your mission.