I think you need to take into consideration that this is designed to be used on voice where the speaker is not aware that they are speaking to a computer (or that they are being recorded at all).
When people talk to Siri, Cortana, or Dragon, they take unnatural care in the clarity of their speech compared to normal talk only meant for humans. Also the speaker may not have been speaking directly into a microphone, lots of background noise, etc.
All of these factors probably combine for a much lower accuracy than what Apple, Microsoft, and Google are going to be dealing with in usual cases. Also keep in mind they all have incentive to inflate their own products accuracy score. Not that the same incentive doesn't also exist for this company/product.