Basically, every new platform has bugs and unfortunately Ryzen still has numerous bugs that can't be resolved via a simple AGESA firmware update, and this is the price you pay for being an early adopter of new tech. The new B2 stepping seems to focus primarily on Uncore and SoC related errata, CanardPC claims they don't see many fixed bugs within the core itself.
The Ryzen B2 stepping may fix issues related to the PCI Express controller or perhaps deliver further improvements for the memory controller, but it will not deliver higher performance.
Ah tiens : stepping B2 en approche pour Zen. Il fixe de nombreux bugs hardware.— Canard PC Hardware (@CPCHardware) 17 juni 2017