Intel had a single-threaded performance lead prior to Zen 3 but it's not entirely accurate to say they had an IPC lead. Zen 2 was fairly evenly matched vs. Intel's latest in IPC, but Intel's clock advantage made overall single core performance clearly in their favor.

So Zen 2 would be when AMD "caught up." Zen 3 would be where they surpass (assuming reviews match the claims etc etc...)