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??"
Many flatpaks are not aware of their sandbox and thus have a bad ux.
E.g. flatpak Steam can't access SteamLibraries at a non-default location, unless the user manually allows the path through flatseal. The same is true for other similar apps which don't use the file portal.
Issues like this are unexpected for new users and thus it can be argued that flatpak aren't a good recommendation for new users. I personally disagree because most flatpak work flawlessly and work everywhere independent of a users distro.