As someone who travels to the United States from Canada on a very regular basis, this does not surprise me at all. The first mistake he made was to say that he was "self-employed". That one little phrase, from my experience, sets off a very large red flag and almost always ends with being secondary'ed and very likely a complete entry denial.
Generally, every question that the CBP agent will ask revolves around money: who pays your salary, in what currency, are you attempting to get in to the USA to find a job, will someone be giving you money for whatever reason (e.g. honorarium for giving a talk at a conference), etc. Additionally, trying to explain the concept of telecommuting to an agent is usually a lost cause.
Canadians do have a slightly easier time getting in & out of the United States, but only marginally.
Generally, every question that the CBP agent will ask revolves around money: who pays your salary, in what currency, are you attempting to get in to the USA to find a job, will someone be giving you money for whatever reason (e.g. honorarium for giving a talk at a conference), etc. Additionally, trying to explain the concept of telecommuting to an agent is usually a lost cause.
Canadians do have a slightly easier time getting in & out of the United States, but only marginally.