Sonoff Vs Tuya temp and humidity sensor

Hi, I have got a Sonoff temp and humidity sensor, and I have bought 5 tuya temp and humidity sensors.
unless I have some problem with Tuya sensor (I ordered Zigbee version and it seems that they work only in wifi btw…).
Tuya are linked via app and Tuya cloud (wifi…) and sonoff are linked via ZHA integration (with conbee 2 dongle).
I put 2 tuya and 1 Sonoff together and I read:
1° Tuya 19.8 °C
2° Tuya 19.9 °C
Sonoff 19.6 °C
Temperatures are pretty much the same.
1° Tuya 66% humidity
2° Tuya 65% humidity
Sonoff 72% humidity

How is it possible? Tuya may be all set with the same parameters and use the same chip and sensors but how is it possible that the measure is less compared with Sonoff sensor?

Another question: what is the update time of the tuya sensor?