You really should ask this in
https://lemmy.ml/c/grapheneos.
It’s a very helpful community. Someone will either explain why or point you to a FAQ. I bet it has something to do with the built in reader being insecure.

GrapheneOS [Unofficial] - Lemmy
### Welcome to the GrapheneOS (Unofficial) community This feed is currently only
used for announcements and news. Official support available on our forum and
matrix chat rooms - Discussion Forums [https://discuss.grapheneos.org] - Discord
[https://grapheneos.org/discord]
- Matrix Community Space [https://matrix.to/#/#community:grapheneos.org] -
#general [https://app.element.io/#/room/%23general:grapheneos.org] - #offtopic
[https://app.element.io/#/room/%23offtopic:grapheneos.org] GrapheneOS is a
privacy and security focused mobile OS with Android app compatibility. Links
- Website [https://grapheneos.org/] - Features overview
[https://grapheneos.org/features] More Site links - Install
[https://grapheneos.org/install] - Build [https://grapheneos.org/build] - Usage
guide [https://grapheneos.org/usage] - FAQ [https://grapheneos.org/faq] -
Releases [https://grapheneos.org/releases] - Source code
[https://grapheneos.org/source] - History [https://grapheneos.org/history] -
Articles [https://grapheneos.org/articles] - Donate
[https://grapheneos.org/donate] - Contact [https://grapheneos.org/contact]
Social Media - Mastodon [https://grapheneos.social/] - Twitter
[https://twitter.com/GrapheneOS] - Twitter Community
[https://twitter.com/i/communities/1530455827949273094] - GitHub
[https://github.com/grapheneos] - Reddit [https://reddit.com/r/grapheneos] This
is a community based around the GrapheneOS projects including the hardened
Android Open Source Project fork, Auditor, AttestationServer, the hardened
malloc implementation and other projects.