Largely true. If you are at Google scale, odds are you have mixed fleets deployed. Such that it is a bit of involved process. But it is well defined and doable. I think a lot of us would rather not do a dance we don't have to do?

Sure, you just have to balance that against the cost of a poorly specified API interface. The errors because clients aren't clear on what is really required or not, what they should consider an error if it is not defined, etc. And of course all the boilerplate code that you have to write to convert the interface model to an internal domain model you can actually use inside your code.