Assuming that Tmall stands alone. It doesn't.
Every permutation of buying and selling between individuals in China is represented. Here I can buy direct from brands AND factories.
When shopping, 90%+ of Chinese consumers use mobile #Taobao to browse, interact, purchase, and write reviews. This is because Taobao is a platform where you can get access to ALL Alibaba channels (e.g. Tmall, Tmall Global, Tmall Supermarket, Suning, etc).
It's an 'All Inclusive' platform. The largest and most successful online marketplace on earth. If you don't believe me, simply take a look at Alibaba's annual report or analysts who cover it.
Look for GMV data for every channel owned by or integrated into the Taobao marketplace. Then add up the numbers.