First one is simple and focused, the second one tries to be & do everything. And frequently never ships.
Their TUI[1] is planned to use react(!), to share logic with their BrowserUI[2]. In the repos you can see how they struggle to get anything gpu backed done (which is required by the browser). Then falling back to wayland to do it for them. (This all seems a mess that LLMs can't figure out.)
Anyway, it does seem to end up in a custom linux desktop environment, with lots of sharp edges that makes it less hackable.
[1] https://docs.flipper.net/one/cpu-software/flipctl [2] entirely unclear why a terminal is insufficient for networked TUIs
First time I've heard anyone call the Flipper Zero "simple" and "focused", most people seemed to have considered it a "swiss-knife" meant to just house a bunch of features and radios, meanwhile the One has less features but more connectivity and I/O.
But apparently you're not alone in feeling this, but I don't understand what from the submission makes you and others believe so, what exactly gave you this impression?
And this one is an 8-core Arm computer and the project has ambitions of some notoriously difficult things: no binary blobs, full mainline support (including a NPU), reinventing small-screen UI for more serious handheld computing, and supporting a ton of high-bandwidth interfaces.
This is not a simple step up in difficulty.