Not updating widget with Thema watch face. Reply from them:...
The watch face uses the raw data sent by the sensor. But
obviously the raw data sent by the hardware to the Android OS is not very accurate. The difference in what you see when you tap the widget is because the data displayed is then displayed by Samsung Health . It seems that they do not use the same way to access their sensor. I mean that they are not pulling their values from the Android layer.
The best way to get the same values as the one displayed when you tap the widget would be to display the heart rate with "complication" linked to Samsung health heart rate data.
Unfortunately, for now, the Samsung Health heart rate complication data behaves more like a shortcut to their app.