Imagine your friend that does not know anything about linux, don't you think this would make them not install the firefox flatpak and potentially think that linux is unsafe?
I ask this because I believe we must be careful and make small changes to welcome new users in the future, we have to make them as much comfortable as possible when experimenting with a new O.S
I believe this warning could have a less alarming design, saying something like "This app can use elevated permissions. What does this mean?" with the "What does this mean?" text as a clickable URL that shows the user that this may cause security risks. I mean, is kind of a contradiction to have "verified" on the app and a red warning saying "Potentially unsafe", the user will think "well, should I trust this or not??"
They should not be worried, they should be educated.
If you worry a new user enough they'll go back to Windows or Apple because there's less scary warnings there.
We need to make the transition as pain free as possible. Learning about the joys of kernel compilation and SELinux can come later.
The first step is "Hey, this is as usable as Windows, without stupid ads in the start menu.