After speaking with AMD tech support, I was told that Precision Boost Overdrive is available on all 2nd generation Ryzen chips.
My Ryzen 5 2600 and MSI B450 Mortar (BIOS version 1.40) doesn't appear to allow for modification via Ryzen Master of the Precision Boost Overdrive settings.
As per this thread, the solution does not work. This is a fresh install of Windows 10 1809 build. I have tried Auto, Disabled, Enabled and Manual in the MSI BIOS to try to alter this.