I've heard back from the customer service people at Casio Japan, and have learned from them that Casio does not put double-sided anti-reflective (AR) coating on any of their high-end Oceanus watches--only single coating on the inside of the crystal. (And, I would guess that this means that they don't put it on their other watches either.) I was a little surprised to learn this. I think their reason is that outside-crystal AR coating can be scratched.
There are two schools of thought on the desirability of double AR-coating, with those in favor liking the greatly reduced reflectiveness it affords (I'm in this camp), while those opposed noting the susceptibility to scratching. I now have two Oceanus Manta models (OCW-S1050 and OCW-S1100) and would dearly love to be able to get the sapphire crystals double-coated. However, Casio has informed me that they won't do this. One alternative would be to go with an after-market AR-coating specialist, I guess, but the crystals seem to be almost integral with the case with each watch, so I'm not sure that the crystal could be isolated for coating.
If anyone has any suggestions or more detailed information about the case/crystal units of these Oceanus Manta watches, I'd really appreciate hearing from you.