In humans, an embryo doesn't even enter the fetal stage until 11 weeks into the pregnancy[...]
Er... I think you're wrong on that one. Once an embryo developed the beginnings of all the major organ systems it's called fetus - and that happens at around 8-9 weeks into the pregnancy...
said it begins 9 weeks after fertilization but at the beginning of the 11th week in gestational age. Evidently I misinterpreted that, since gestational age is counted from the start of the previous menstrual period, which apparently is traditionally assumed to be two weeks before fertilization. So you're right. So the fetus would've been 12 weeks old and thus in its "14th week" of gestational age.