She is making a statement with the photo: she is young (age 26), beautiful, and as a proponent of attachment parenting is unashamed/unapologetic that her son still breastfeeds. She goes against the stereotype of the 'slightly odd earth mother granola-munching hippy' that many would think typically do extended breastfeeding.
Of course she doesn't feed him like that normally - she is striking a strong and even defiant pose for those who would criticise or judge her choice.
I am in America, and she has been giving interviews about who she is and why she did it. She has stated that she was breastfed herself until age 6, and wants to do the same for her dc until they self-wean.
By striking this pose with her son, the subject now is 'controversial'. A more traditional photo would not have caused uproar, and would not have brought this sort of attention into the general arena for discussion.
I think the more important issue here is the 'Are you Mom enough' headline. It is asking if you are 'hard core' enough in your support of attachment parenting to commit to extended breastfeeding.
Clearly many Mums simply wouldn't want to breastfeed until their child self-weans (and we can discuss why/why not, and their needs/wants vs those of their dc), and others might want to but simply can't due to working schedules, etc. Does that make anyone a less committed Mum? And why are those who do extended breastfeeding often perceived as 'weird'?