I do feel there's been some confusion in regards to what the UI Scaling Options entail and these could maybe be made a bit clearer by re-labelling the UI Scaling Options.
To give a rundown, PSO2's UI defaults to the reference resolution of the size it was created for (1280x720) which makes the HUD appear small on devices with a larger resolution. The maximum scale the UI can go on any display is the size it was originally designed for. The result? In terms of physical space, "Middle" on a HD TV and "4K - Large" on a 4K are the same, what actually changes on a 4K display is just how small the HUD can go. The fact that the game defaults to the smallest option (which can have different sizes if you are playing on a HD or 4K TV) and the way the HUD options are labelled has been a source of minor confusion (and in some cases, even misinformation) amongst several people wishing to try out the game.
My suggestions as such are as follows:
Make the game default to its largest UI size available by default. This also doubles as an accessibility consideration as the game's HUD when set to "Small" can be unreadable to some players, making it difficult to find their way to the UI Scaling menu to resize it.
On a HD display PSO2 PC features three scaling options (Default, 1.25x, 1.5x). Im assuming on Xbox One, "Small" is equivalent to 1.25x and "Middle" is equivalent to "1.5x. Given that 4K has the three "Small", "Middle" and "Large" scaling options, it would be nice if for the sake of consistency (and more options for HD displays) the full "Default", "1.25x" and "1.5x" were available on HD displays as "Small", "Middle" and "Large", bringing the total amount of Scaling Options to six instead of five.
It would be nice if the Scaling Option menu were a slider instead of a drop down selectable option. The slider could always be one based on preset positions (three for HD, six for 4K).