Ragemage
Wept for Zion
snip
I don't need a citation to show Synths run off machinery, we know for a fact they do. You don't just go from a Gen 2 Synth to magically making people. Synths aren't test tube babies. They are not biologically made. Do they have biological parts? Yes they do. Are they entirely biological? No they are not. Though if you do want a "citation" literally every single Institute scientist that works in the Synth retention department and the Synth building department believe Synths to just be MACHINES. Not people. Thus why they treat Synths the way they do, and those are their creators. You can't get a better source than the literal creator of these things.
And I just told you what percentage of the people Covenant bring in turn out to be Synths, 1 in 4. Roslyn says it herself if you go through her dialogue options during her associated quest. She says the variables used to be worse but she's clearly narrowing down what differentiates a synth from a normal person. She was right about Anna after all.
Thing is, we don't know enough about the Synth component to know what it truly does, but we can assume it works like a vital organ because ripping it out kills them instantly. It doesn't just lower their health, make them go unconscious, or anything of that nature. They just die immediately. I wonder now though, since it doesn't cause any blood/loss of limbs/etc when you steal it, if the component is actually on the outside of the synth? Would explain the lack of anything falling apart. If it were inside I would think when you take it out of a living Gen 3 synth they would fall apart like when you cannibalize someone in FO3.
"But considering it's impossible to determine, even for the Brotherhood of Steel under a microscope, whether or not someone is a Synth" Citation needed. For that matter the synth component basically proves whether or not someone is a synth so that's a completely false statement.