Since Bisq and Agoradesk are the most popular platforms, I will mention about their terms.
4. Responsibility of Website Visitors
Moderators have not reviewed, and cannot review, all of the material, including computer software, posted to the Website, and cannot therefore be responsible for that material’s content, use or effects. By operating the Website, forum operators do not represent or imply that it endorses the material there posted, or that it believes such material to be accurate, useful or non-harmful. You are responsible for taking precautions as necessary to protect yourself and your computer systems from viruses, worms, Trojan horses, and other harmful or destructive content. The Website may contain content that is offensive, indecent, or otherwise objectionable, as well as content containing technical inaccuracies, typographical mistakes, and other errors. The Website may also contain material that violates the privacy or publicity rights, or infringes the intellectual property and other proprietary rights, of third parties, or the downloading, copying or use of which is subject to additional terms and conditions, stated or unstated. Forum operators and moderators disclaim any responsibility for any harm resulting from the use by visitors of the Website, or from any downloading by those visitors of content there posted.
21. Survival
If any of provisions aforementioned in these Terms of Service are to be found void, invalid, unenforceable or illegal by a court of law, validity and enforceability of other provisions shall not be affected in any way. If any provisions are to be declared unenforceable, you agree to an amendment made by Blue Sunday Limited to provide for the enforcement of those provisions to the fullest extent permitted by applicable law.
Using their platforms in order to stay private is easy, but if you use it to mix your coins, it's not going to be easy as you might leave your trace somewhere else.
If there are only few users who trade on the pair you use, it will be easy for the exchange to know which one is your transaction.
If you send 0.5 BTC, you convert to XMR and you convert it back to BTC, now you have 0.48 BTC (fees deducted), then you withdraw that 0.48 BTC at once, they might recognize you since the amount is almost same.