Maybe I’ve misunderstood, but how much differs between these and the earlier certification for the parts of these? Clearly the control car is new and needs to be certified, but the regular Venture cars are already in service, as are the locomotives. (And the future pantograph cars and the locos which can take power from them would clearly need certified too, but that’s not about these sets specifically.)
I could well imagine Amtrak wanting to hold Siemens to a high-bar especially for first-of-type testing, to ensure everything works well together per contracted specification, but that isn’t a (FRA) certification matter.