> is there anything that would make such embryos more "slaves" than embryos or fetuses in a womb?

Arguably much-less-so, given the complicated and morally-ambiguous mechanics of primate gestation [0] where a fetus in the womb exercises a degree of biochemical control and extortion over the mother.

[0] https://aeon.co/essays/why-pregnancy-is-a-biological-war-bet...