Data scientist means someone who's had classes in stats and knows how to use software to analyze data. They don't cover how to run experiment and don't cover ethics
To be fair, the profile of a data scientist at a F500 non tech company and at a company like FB is slightly different. Facebook's data science crew is known for being heavier on the stats lighter on the software (relatively speaking) and probably can design a good experiment.
That said, anyone who signs up for a job at Facebook doesn't give a shit about ethical design of experiments.
Hi, I used to work on ML and ran experiments like this one at FB. Just want to point out that the effect of experiments like this on an individual is smaller than the effect of making the app start 0.1 seconds faster, or retraining the network used to filter hate speech. The only reason the effect is significant is because N>650k, so tiny effect sizes can be detected.
That said, anyone who signs up for a job at Facebook doesn't give a shit about ethical design of experiments.