Intel, AMD, and Nvidia have one thing in common; they usually pick a "best case scenario" when displaying their new tech, Nvidia cherry-picked games when showing off Turing, AMD did it with Radeon VII with very few games and now with Zen 2 with Cinebench and Blender. The benchmarks might not be fake, but they are usually a little on the optimistic side.
So when Intel claims an 18% "IPC" gain for Ice Lake (-U/-Y), I will take it with a grain of salt. But still, Sunny Cove is a major architectural overhaul, and even if the real gain is more like ~12-15%, it's still very good and would be comparable to Sandy Bridge -> Skylake.
But remember, this is just the low-power variant. I'm more interested to see the improvements for Ice Lake-SP, which have a different cache configuration, memory controller and various core features.