I think the numbers are fudged because of the "definition" of a smartphone. Most Japanese phones are probably considered media-phones or enhanced-phones.
"The MCPC believes that there is a difference in smartphone usage patterns between Japan and Europe/North America. Smartphones in the West have become popular as a device for email and other communications as compared to the voice‐centric nature of regular mobile phones. In Japan, mobile phones have been designed with advanced functionality, including i‐mode, picture mail, official websites, etc."
[About half-way down] The iPhone is less than 10% when compared to more realistic competitors.