I think it's not the JASO that's as important as the MA that follows it - wikipedia says this [remembering that the 919 is definitely a wet-clutch engine]:
The Japanese Automotive Standards Organization
(JASO) has created their own set of performance and quality standards for petrol engines of Japanese origin.
For four-stroke gasoline engines, the JASO T904 standard is used, and is particularly relevant to motorcycle engines. The JASO T904-MA and MA2 standards are designed to distinguish oils that are approved for wet clutch use, and the JASO T904-MB standard is not suitable for wet clutch use.
For two-stroke gasoline engines, the JASO M345 (FA, FB, FC) standard is used,
and this refers particularly to low ash, lubricity, detergency, low smoke and exhaust blocking.
These standards, especially JASO-MA (for motorcycles) and JASO-FC, are designed to address oil-requirement issues not addressed by the API service categories. One element of the JASO-MA standard is a friction test designed to determine suitability for wet clutch usage.
An oil that meets JASO-MA is considered appropriate for wet clutch operations. Oils marketed as motorcycle-specific will carry the JASO-MA label.