"Luke is one of the only people in the world to earn a certified Brazilian Jiu-Jitsu 2nd Degree Black Belt without a BJJ Instructor!"
Yeah, this was the statement that was sketchy to me. The fact that he keeps saying "certified" everywhere makes me tend to not believe it. When you overstate something, you're usually lying about it. Like, if you came up to me and said, "I don't like cake." And then five minutes later said again, "Cake is disgusting, isn't it!" And then I find out that my cake is gone. Sure, cake is so nasty.

Most instructors just say, "Hey, I'm a legit BB under [fill-in-the-blank]."
I researched some more and after my research, I would say it looks like he's legit. I found old, old forum (2005) posts talking about Luke Rinehart in competition. Says, "Pablo Popovich vs. Luke Rinehart: POPOVICH by Points". If he only lost by points to Popovich, then he's most likely legit. Also, if I remember correctly, the whole IBJJF certification for black belts happened in January of 2011. I found some articles that state that Luke Rinehart competed in the NY Open in April of 2011, so he had to be certified by someone.
However, I'm not a big fan of all the spammy looking sites. I even found a book by him called, "Financial Jiu-Jitsu: A Fighter's Guide to Conquering Your Finances" that is advertising his site. He also seems to have a lot of spammy landing pages set-up all over the place. Not a fan of that, but he appears legit.