Let's say your definition of the phrase 'choice feminism' is accurate. I submit that your question falls if considered under certain realistic circumstances. For one, (I assume) you are comparing the mental status and choice of a slave long conditioned to his/her position of subjugation whilst possessing little to no recourse to an alternate lifestyle to the mental status and choice of a woman who has not been subjugated or physically kept subservient and also is aware of her potential, innate worth and alternate lifestyle choices. There is an argument of similarity in that, the woman and slave were born into situations where their minds are conditioned to prefer certain things but I think the degree to which the two are comparable is so remote that it is almost absolutely unusable. I assume you are talking about an educated woman in a modern, first-world setting.
Realistically, it is acceptable for women to take on these roles because these roles must be fulfilled, whether it be by a woman or a man living alone or in a family. Someone's gotta clean the house and when we tell a family outright that "when a woman does it, the woman is oppressed", I think we are helping nobody. Also, not many people say that a man is oppressed if he chooses a traditional male role and almost nobody demands a man justify his lifestyle choice, so why are we demanding this extra bit from women ? Isn't that a form of oppression ? I've read people arguing that mens' choices aren't questioned because they've traditionally had more of them and women have had less. That may well be true in some places of the world but that doesn't cut it for me in this instance unless we can show the possible choices of a woman to be demonstrably less than that of a man, don't include trends and general statistics of crowd choice. Asking a woman to justify her choice of lifestyle while having no evidence that she is under compulsion or coercion is antithetical to the concept of allowing women greater freedom.
I also disagree that nobody would have argued for "choice anti-slavery". In fact, it could be argued that it's cruel to forbid people who have been enslaved for a long time to work as indentured servants (maybe not work for the same person but that's beside the point) because sometimes, that's all they have to move on to greener pastures or a different country. As FreeElk pointed out, the lack or prohibition of choice is the greater oppression here, not the choice or task itself.
Secondly, by telling a woman who chooses traditional roles that she shouldn't choose them or that she is no feminist if she does, we are essentially claiming that we know her mind better than she does. We are telling her that someone other than herself understands her situation, thought-process, knowledge and judgement better than she does. While this can sometimes be true, it almost never works when pressuring a free woman to commit to a lifestyle she does not want. The autonomy puzzle is solved when we consider women to be as un-brainwashed as we are (a given concession in almost all cases, I say). I think it's a little condescending to consider women to know so little about themselves and their choices while giving ourselves free rein to pronounce their positions and choices as contradictory. From a purely philosophical standpoint, we are asking women to prove their self-awareness and sovereignty of choice.
if women represent an oppressed category, isn't this notion contradictory?
Yes, if most women can be shown to reject traditional roles to a very high percentage the moment they are presented with alternate choices and understand them, your statement would hold true. As it stands, not all women are as oppressed as the rest of them and there is nothing contradictory about choosing A or B out of the alphabet of their available choices whilst claiming they are feminists. Whether or not those choices are indeed available to them is another question.
Traditional female roles aren't any more oppressive to women than traditional male roles are to men. The oppression comes when you force someone to choose something they do not want or tell them that they cannot choose something, injecting unwanted hardship that cannot be avoided. Feminist philosophers do not have to justify "choice feminism" because some of the most widely accepted tenets of feminism include seeing women as sentient, mental equals, allowing them their choices and subsequently respecting said choice. I realise that there is an argument to be made for women who are genuinely "brainwashed" but you'd have to be some sort of psychological expert to make that call. I could be wrong but I think as a general rule, if a woman somewhere is free enough to openly call herself a feminist, then there's nothing wrong with her then choosing a traditional female role.