I tend to disagree with this statement. As a market researcher the general consensus on forums is that there is a pool of negative users, this creates a skew in research data. Consumers typically set the bar very high to post positive and influential information. The product must almost be absolutely flawless and satisfy various hierarchy levels of self realization before considered perfect. While for negative issue the bar is set very low, where people will light a forum or discussion up about anything negative.
Personally I would be safe to say that iPad Pro is selling excellently for numerous reasons. The Apple pencil is nearly impossible to find, this means Apple underestimated their attachment rate to iPad Pro. This means Apple the company they are use the just in time (hybrid JIT) manufacturing practice and they did not predict the overall popularity.
Another prevelent sign Apple iPad Pro sold well, and can disprove Apple attempted to create artificial demand (some people believe they do, I do not its bad business practices) most retailers such as Bestbuy who sell accessories are picked clean of accessories for the iPad Pro. This means that the secondary party attachment rates were underestimated as well.
This can all be here say, but I believe wholeheartedly with my supply chain management experience and marketing experience that the iPad Pro is sellinb beyond Apples estimated target.