In this case, "resonate" is to agree with. Have you ever seen an opera singer break a wine glass using only her voice? That effect uses resonance of sound, but the use in your sentence is similar. Person B's "definition of high performance" _moved_ Person A in a way that was deep and natural. English has a phrase involving two people "on the same wavelength", meaning they think or feel similarly. That phrase also borrows the science-of-sound to express a feeling.

Resonance is a common vibration so it means two things move in unison so when something “resonates” with you, you understand, feel in common with or can sense it without explanation or problems. So in this sense it may mean understanding or in agreement.

I guess that it means almost the same as "sympathize with" in this context. Imagine they play various kinds of musical instruments in perfect harmony in a symphony orchestra.