That might well be true. The number sounds plausible.
But it doesn't mean that 22% of e-commerce sales are done from smartphones. I haven't seen any figures on this, but I suspect that many people will be comfortable doing basic web browsing and searching from a mobile device, but might be reluctant to complete a financial transaction in that way, especially if it involves entering detailed or sensitive information.
Of course, that will inevitably change over time, as more and more consumers give up using a desktop PC or laptop in favour of a hand-held device. Mobile e-commerce is not something you should ignore.