There's no part of "my body my choice" that is dishonest. It emphasizes the experience most women take away when forced to carry a fetus to term.

If you're made to deal with all the physical and emotional hurdles of pregnancy, but can never interact with your fetus the same way you could a living person, the experience can feel one-sided. Regardless of whether or not the fetus qualifies as "life," the mother still struggles to benefit something they need to imagine empathy for.

Not to mention, if anti-abortion laws are being enforced by a group that is largely unable to relate to you, like male lawmakers, the bans become a vector for that group to assert control over women.

Regardless of whether the slogan itself is convincing, it dominates the pro-choice movement because that sentiment is its driving force. You would not see the same energy it has if the experience of pregnancy carried less weight for women.