That CPU comparison is mostly based on single-core performance but I'm considering the chipset as a whole. Honestly, one of my thoughts when they released the 2018 iPad Pros was they're closer to replacing Intel on Macs than I had originally expected.
Apple switched from homogeneous to heterogeneous processing on the A12X (well, A10 -> A11 really) and I believe they increased from 6-core to 8-core so multi-core performance increased by 100%. A12X is also when they added the Neural Engine on iPad. They also improved storage performance, and yes, that was mentioned in keynote although they never really go in depth.
Here are some SSD performance benchmarks of the 2017 iPad Pro 12.9 512GB and 2018 iPad Pro 11 1TB.