Alright, in the same blog post as mentioned in the previous item AMD also talks about a Temperature Reporting Offset. This one was new to us, but basically what they claim is the following. To keep a "consistent fan policy," AMD is forcing 20C offset on the Ryzen 1700X and 1800X processors. This makes them report temperature a good 20C above what the sensor reads. 

All models on the AM4 Platform have the same maximum tCTL value.

Temperature Reporting

The primary temperature reporting sensor of the AMD Ryzen™ processor is a sensor called “T Control,” or tCTL for short. The tCTL sensor is derived from the junction (Tj) temperature—the interface point between the die and heatspreader—but it may be offset on certain CPU models so that all models on the AM4 Platform have the same maximum tCTL value. This approach ensures that all AMD Ryzen™ processors have a consistent fan policy.

Specifically, the AMD Ryzen™ 7 1700X and 1800X carry a +20°C offset between the tCTL° (reported) temperature and the actual Tj° temperature. In the short term, users of the AMD Ryzen™ 1700X and 1800X can simply subtract 20°C to determine the true junction temperature of their processor. No arithmetic is required for the Ryzen 7 1700. Long term, we expect temperature monitoring software to better understand our tCTL offsets to report the junction temperature automatically.

The table below serves as an example of how the tCTL sensor can be interpreted in a hypothetical scenario where a Ryzen processor is operating at 38°C.

AMD Ryzen 7 have a Temperature 20 Degree C Reporting Offset