Idemitsu makes at least 3 different 0w20 oils (at least it did in the SN versions).
They make a dexos licensed version, a high-moly version called 'Zepro', and their 'regular' version which is pictured in this thread.
It has been speculated that their high-moly version is the same as Mazda's OE oil. The one pictured in this thread is NOT that version.
I actually scored a few 5 quart jugs of that 0w20 (the one pictured in this thread) in the SN version (not SN+) for $5 each at the AZ 'CLEARANCE' last year....I haven't used it yet so I can't comment on how it runs.
PS: The Miata isn't turbocharged so I'm thinking that OM is saying that any 0w20 synthetic....even SM rated as long as it has the 'starburst' symbol...will work. I'd use Mobil 1 Advanced Fuel Economy and feel good about it.......
Here's the high-moly version which is thought to be the same as Mazda OE 0w20....it actually says that it is the same in the 'questions' about the product on Amazon:
https://www.amazon.com/ZEPRO-300100...18603548&sprefix=Idemitsu+0w20,aps,924&sr=8-3