That’s not true. Roblox doesn’t automatically set the scale for UIs. You always have to set it yourself or use a plugin like AutoScale.
If you want to scale the UIs yourself, you need to remove the offset completely, and adjust the scale of the size of the UI so it fits the screen. Once you SCALED the UI (not positioned it), to your liking, it will fit for all devices.
Once again: Moving the position will not scale it for all devices.
You need to go the properties of the UI, remove the offset completely, and use the x and y scale to fit it to your screen. Then, it will fit all screens.