I had recently installed Grapheneos on my pixel, with a goal is determining what was responsible for all the senseless Google domains that a pixel normally contacts.
To my surprise disabling Network for the Google Services Framework and Play Services killed all of the nonsense. The only downside was that GSF has the push mechanism in it also, that many apps use for push notifications.
If only there were an alternate for push notifications that all apps would use.
Anyway, Grapheneos runs way cooler than Google's Malware version.
So it might be that Fairphone is not aware how to make the notification bar transparent. It's a setting in android development they can enable. (Disclaimer: I'm not a developer.)
With that in mind, they seem to be saying it was intentional to hide their lack of knowledge. It's simply unreasonable that any developer would want such a hideous defect permanently at the top of the home screen.
On a positive note, I believe android 15 is supposed to correct this when the developer does not.
You're not likely going to get any real help since you're insisting on using the browser in an extreme and unconventional way. Your little world is just one browser/OS crash from losing all of those tabs.
That looks nice, but apps that use GSF for push won't use that. Or am I missing something on their website?