Directly dispatching a function via a call per the ABI of your computer vs producing a serialized message stream, sending it to another process, deserializing a stream and then calling the function.
Yes, it's less efficient.
The better question might be "did it matter in practice?".
I once replaced an export operation that depended on COM calls to Excel with some text manipulation code and brought the run time down from 30 minutes to an hour to just a few seconds. So in at least that case it did matter in practice.
Yes, it's less efficient.
The better question might be "did it matter in practice?".