I do understand a certain 'paranoia' regarding sensors, as they could collect very powerfull data, especially when combining them.
An example of what could be derived from sensors alone: https://github.com/phyphox/phyphox-android
What u brought up, that if for example i've created a 'malicious' app with the purpose of extracting data obtained by your sensors on your phone, i've could indeed store that data on device and send it back to a server IF there comes a internet connection available.
As far as i'm aware, GrapheneOS is the only OS that lets u revoke apps acces to the sensors, and i believe GrapheneOS does this by default for third party apps by default since a while
As @Xtreix mentioned, i would advice not to disable sensor acces to system apps, as they could break functionality, it wouldn't be beneficial in any way aswell, as GrapheneOS doesn't collect that data anyway.
So, to answer your question 'Tracing sensors totally of on GrapheneOS'; Yes, GrapheneOS doesn't collect data about sensors, and a potentional app who might is revoked by default.
If u are worried about that, it's best to only use 'trusted' open source thrid party apps who would need acces to sensors.
'Unfortunally' sensors is a broad umbrella, and i believe even a video player would need acces to sensors to be able to auto rotate to landscape mode.
So basicly luckily on GrapheneOS, u can revoke apps ability to acces sensors, in addition to revoke acces to network. If there would be a questionable app u needed to give permission to sensors that perhaps might collect that data, without network it can't be obtained. (Unless there would be IPC possible between that app and another app which had network access).
But if your threat model includes worrying about this specifically, and u only use 'trusted' thrid party open source apps, this shouldn't be an issue.