The main reason TN visa for a management consultant is a heavily scrutinized category under NAFTA is that it is susceptible to misuse and abuse by employers who seek to fill positions within their companies.
The Customs and Border Protection (CBP) inspectors, therefore, must determine that the position you are pursuing is truly a consultant position.
Also, its scrutiny is partially a result of the fact that eligibility for the position does not necessarily require a formal degree; this flexibility itself is considered to be a pitfall.