As you mentioned, the data processing inequality[1] applies here, but I imagine synthetic data could help training squeeze out more from the existing data.
[1] https://en.m.wikipedia.org/wiki/Data_processing_inequality
[1] https://en.m.wikipedia.org/wiki/Data_processing_inequality
It's probably true for people too. Instead of asking an expert for an opinion right away, ask them to discuss the options out loud first.
Also, "natural" data taken from the Internet is probably quite inefficient as training material. It's going to have a lot of duplication. You only need each fact once to be able to synthesize more examples of it.