Although I don’t think being a manufacturer for Scion automatically makes their parts equal to Scion under their own name, I agree with your point “same”. Subcontractors make parts according to specs. required by the automaker.
I say the opposite is often true. I have found for example, in replacing the the rear leaf springs of a Toyota PU, the after market had a better warranty and reputation for being less “brittle” and prone to breaking when off roading. I don’t think it’s an isolated case and feel there are aftermarket parts “superior” often to OEM and or other after market parts makers.
I am no longer impressed by the OEM designation or “name brands” and feel it’s a part particular decision as to which is best for you and your car.