Another point is that the there is a section of audience which doesn't necessarily use smart phones, or won't use smart phones for making such purchases, who now won't access myntra.
Indian e-commerce space is evolving, and with so many players in the field, the ultimate user would explore all the other options before committing to a purchase (unless they are extremely loyal to myntra), and now it seems to me that with the platform restricted to mobile/tab application, myntra has made a huge mistake.
But it would be interesting to see how this pans out.