The word police have not been enforcing the law, so unfortunately for any pedants this change in meaning is likely to stay.
There are still many contexts where if you say NEET people will just think of the original definition, and others where people consider it the shut-in anime one.
Also in Japan it seems the definition is a bit more broad than the acronym (otherwise even housewives would be NEETs): "In Japan, the classification comprises people aged between 15 and 34 who are not employed, not engaged in housework, not enrolled in school or work-related training, and not seeking work."
Self-training is definitely "work-related training". And he was doing housework.
Selling your own stuff is definitely self-employment though.