Because the data for that is *always* not at rest the moment you unlock the device once after boot. On a user profile you can put data at rest by pressing the end session button, you cannot do that for the Owner because the owner manages crucial OS functions. It is how Android works. To put Owner at rest you need to power off the device or restart it instead.
It's a more extreme move but it adds resistance to attacks especially in forensic situations.
i see that makes sense and thank you for explaining. guess better to know now than later. Is there somewhere can learn more for questions, like how do you setup your apps, do you manage them (is updates) in base owner profile, or in each separate one?
guess I just installed it and didn't go too deep reading the instruction manual, I should do that
Many of that depends on users but I would suggest reading the docs and guides on https://grapheneos.org for it. How and where people get their apps is down to who they trust to do the job.
We have expressed interest in adding Accrescent.app (a privacy and security focused app store) as a mirror to our app repository soon. It's app catalogue is very small and it is in early alpha but it's hopeful users add onto it. When that happens we will recommend users to use Accrescent further.
The forums also exist ( https://discuss.grapheneos.org ) as well for user questions
