The problem Ytrumz, is that we don't know if the Synth component is the whole of their brain and thus their intelligence is wholly mechanical, or more likely it is just a mechanical part of an otherwise organic brain.
The Synth component is not particularly large and if it is an anologue to the Android component in Fo3 then it can be removed surgically with no harm to the Synth. All implication is that the Synth component is not their entire brain.
And that is the issue, if Synths have grey matter, as it is likely, then comparing them to robots is a false equivalence. A certain cyborg had chips in his brain too.
If the Synth component is just an IO device for facilitating memory manipulation then the problem remains of when a Synth gains self-awareness, whether a brain bereft of learned experience is self-aware or whether preloading memory counts as learned experience.