Of course it was but with Esau selling his inheritance his entire progeny was affected. But your initial comment that I responded to was "backsliding". Backsliding does not equate to "selling ones inheritance". In other words completely and irrevocably putting this worlds wants or needs ahead of our eternal inheritance.
Here is the key phrase "Thus Esau despised his birthright". Esau didn't just "backslide" from a commitment to his inheritance. He outright rejected it for a momentary need. To equate Esau selling his birthright to simple backsliding presents the wrong picture I believe.
OK, I see what you’re saying, but backsliding is a better term for the danger that Paul was trying to address. It may start with a small departure, but it then advances to bigger and bigger transgressions, and soon all is lost.
We may not know the full story of how Esau got to the point of disrespecting his inheritance, but I tend to suspect that it too was a result of a gradual loss of faith over time, or a belief that he could scam his brother, since his parentage was solid, it is hard to believe that it was a sudden rebellion.