Self employed

Ok, so we’re back to hobby vs. self-employed.  I was told earlier by another expert that if I sell goods for profit, I’m self-employed.  However, I consider what I do as a hobby….no expense records kept.  The response above cites “IF” this is a hobby….which connotes that the taxpayer is able to make a choice, e.g., business or hobby.  Is the choice truly mine or, as stated by another expert, is there no choice and I’m automatically considered self-employed?? And if I get to choose that my side gig is indeed a hobby, then all income over $600 is taxable without the benefit of writing off expenses?  How is that fair??