That's not quite accurate.
2018: +3% IPC (Zen+)
2019: +15% IPC (Zen2)
2020: +19% IPC (Zen3)
2022: +9% IPC (Zen4; AMD estimate)
On average, AMD is hitting closer to 10 - 11% per release, but note how some generations take a while to release (Zen4).
Officially,
AMD's target beat the "industry-standard" 8-10% CAGR (which is IPC + clocks + memory combined).
//
Apple A15 <-> A15 is only a 4-5% IPC increase, which is roughly a "Zen -> Zen+" improvement, e.g., small in IPC. But it has significantly better efficiency and still much higher clocks, so for mobile & laptops, that's a significant improvement.