I think the point is that Feynman came later to contribute to Quantum Electrodynamics, the "first theory where full agreement between quantum mechanics and spec

I think the point is that Feynman came later to contribute to Quantum Electrodynamics, the "first theory where full agreement between quantum mechanics and special relativity is achieved."* * https://en.wikipedia.org/wiki/Quantum_electrodynamics https://en.wikipedia.org/wiki/Quantum_electrodynamics