to properly identify a lot of animals. But, I would be surprised that folks would confuse mantas (Atlantic, Pacific, etal) with other big rays.
However, I HAVE witnessed confusion in identifying sharks. I have a degree in Marine Science (geology/geophysics), but I also have an "unused" degree in biology, with an emphasis on Marine Biology (and an interest in the same). I still have trouble with sharks, especially when they are swimming at me and I am with a faster buddy (you NEVER have to be faster than the shark, just faster than your buddy. A slow buddy provides me with a measure of security. Ha!).
For example, there is a shark on a local dive site that I see almost every trip. I am not certain, that he is the same shark, but the repeitive occurences suggest it.
I have hear him variously identified by other divers as a "big bull", a "tiger", a "sand tiger". a really big "silky" and a "lemon". He is, in fact, a bull, but I only know that because I took a trip with a marine biologist who saw him up close and got a positive ID.
About 3 years ago, I saw what I thought was a bull shark on a winter dive at the Flower Gardens. He was so big, he looked like an airliner bearing down on me. He had a big broad head and a thick body--what I thought was a classic profile of a bull.
When he turned, I snapped off a shot of him with my Nikonos at a distance of about 3'. When the slides were developed, I noticed that he had some faint striping along his side near his tail. What I saw was a Tiger, not a bull, but probably not fully mature.
As for the area in question, the Red Sea, I have no knowledge (I am only jealous that I may never go there). I can't defend the identification of all the critters reported to lurk in that one spot, but I can say that "anything is possible".
I once had someone tell me that "There are no whale sharks, mantas or sharks in concentrations worth seeing offshore Texas.
Yet, on a single winter trip off our coast, I have "communed" with a 12' Manta, drifted off the bottom beneath huge schools of eagle rays and hammerheads, swam in the midst of hundreds, if not thousands, of silkies and heard tales of other divers on the same trip who swam with a 30' whale shark (alas, I missed that...). These trips were "planned" to see these creatures, and while such experiences are not guaranteed, there are common enough for us to reasonably hope for them.
Anyway, anything is possible. Just maybe not always probable.