X370 Fatal1ty Gaming K4 voltage CPU-Z

The issue is coming from the fact that Ryzen is an entirely new platform with a completely new architecture. Monitoring apps have not properly caught up to the changes so these inaccurate readings will be corrected in subsequent updates to monitoring apps. Each manufacturer would have gone about temp sensors in a slightly different way and because it is a new platform the (3rd party) developers that release their monitoring apps have no way to know exactly how it works until they get data back from the field. Whenever people submit a validation on CPUz for example, this kind of info is included in the data sent to their site. It then takes them time to analyze this data and update the monitoring apps.

F-Stream is accurate, ASRock know exactly how their sensors are set up so the readings will be correct. This data is harvested from sensors on the board, each manufacturer will have their own unique layout, sensor model preference and design so their branded monitoring tools will be designed to work with their products. The problem with these tools is that they tend to be more limited than 3rd party offerings and also are restricted to the products they are designed for so for comparative purposes on say a forum, people will prefer a common 3rd party app that works on everything.

So all in all, no, you have nothing to worry about, it will just take some time before all current board models are accommodated by 3rd party monitoring apps 

Thanks you very much for the detailed response, I expected as much but just wanted to validate my expectations :) 

And yes, the Gigabyte boards were also AM4 boards.