Yeah I'm not sure if it is a double standard or even if it just seems to be that the weight loss industry and glossy magazines getting a lot of bashing post body positive movement by the Gen-Z'ers. Because of the negative impact it can have on people's mental health.
I don't think the bashing is so much on the person that loses weight. I see most people get congratulated when making a big transformation. I think the bashing is more on diets and dieting products, weight loss coaches etc.
Diet industry has had a lot of really not great practices such as diet teas, pills, and some very questionable dieting practices. There is a lot of terrible advice and products out there which has lead to the anti diet movement being 'in trend'