It's weird wording, but that's common with Nissan/Infiniti. I think it means that the minimum specification is conventional, and you don't have to use synthetic. Of course, this makes great sense, because what really is a synthetic? If they wanted something more "advanced" than ordinary 5w-30, it would be prudent to call for a specification. With 0w-20, the average person is going to run into a synthetic anyhow. With 5w-30, well, you know how that goes.
For reference, Infiniti/Nissan in Canada use Mobil products as service fill, and they go through plenty of M1.