There’s a big difference between a person’s DNA and a person’s art. DNA is the principle part of someone’s biometric identity, which can be used to reveal an enormous amount of information about a person. Hence it is not unreasonable to expect that its usage will be handled in a careful and clearly defined manner. Most countries have very strict laws on biometric data for a reason.

The same can not be said for a piece of art. While an an artwork will often convey aspects of the artist’s personality, and can conform to an identifiable style, it would provide no where near the level of insight into a persons physical identity as a DNA sample.

It also seems a stretch to conflate sharing something privately and publishing something publicly. The former will have expectations of privacy and control, regardless of whatever is stated any legalese incomprehensible to the average person. The latter however assumes a loss of control, to share something publicly is in some ways to cede it to the public.