Every ostensible use, by Person X, of another Person Y, in order to produce a work of art (which itself would presumably produce some impression, of any type - positive or negative; love or disgust or anger; whatever) is abusive. It is always a use of people not for what they are but for what they can (or cannot) appear as, or appear to do. There is no way out - even candids are not an escape route because they still presume that the observer doesn't know they are being watched, rendering consent outright impossible, even for instances where it would have been granted otherwise.

The gentlest, most caring photographer is abusing their models too. They are only being nice about it.

Eva excepts painting and sculpture - but that is a modernist bias. Painting and sculpture have lost a place as strong cultural signifiers only because today photography is more available. It has also meant that the artist is keener to take liberties with the realistic aspect of the final piece, so it might not resemble the model closely - there is an increasing separation of roles between the photographer and the painter / drawer and sculptor. But the artist is abusing their model equally in them. The chances that the piece resembles the model less seem to me to be a weak ground to say that painting and sculpture are less abusive, given the same creative process of use for appearance rather than essence.

There is also the issue of memory, and the artistic experience can be particularly intense in manners that other experiences might not; but while it might alter the perception post facto, and especially long term post facto, that the former child subject has of their participation, it has no bearing on the abuse taking place upon production - that is going to be present whichever the memories come to be. That was present also for the former child subjects who remember it with a positive leaning.

There is, finally, the issue of whether art, even as inherently abusive, is more abusive or not than other activities. I would say that although school or sports need not be abusive per se, unlike art, both tend to be more abusive than art is, in most of the real life settings in which children engage in either. Junior leagues and competitions on the one hand; and the mind-numbing and hostile environment of school on the other, are more abusive to more children than participation as subjects in art has been to other fewer children. Imho.

But while all of these are valid issues to ask regarding any case and regarding the question of which is worse in theory, they only give a greater palette of shades of grey-to-black but don't disprove that it's never white.