The value you see in the barometer section is the raw data that the sensor outputs. There is no calibration on that side. You can check this by using another app that shows the sensor data. In my huawei watch 2 I used to have a test mode hidden in the settings where I could see all the sensor values, including the barometer.
As you said air pressure decreases when climbing up, so it might be that the station is at a lower altitude than you are now. If you live in a hilly city this is plausible. But these are just assumptions.
My weather station is 3 meters above me, and 10 meters in horizontal plane My other watch (TicWatch 3 Pro) shows 1025 hPa correctly and automatic Calibration works there.
But inacurate pressure is not the problem - real problem is why automatic calibration doesnt work on Watch4? I've tried rebooting and connecting with wifi with no luck...