You can redefine your coordinate system and view planes at any time, so I don’t know that it matters a whole lot.
Horizontal / vertical are sketch shortcuts when sketching, you could use parallel and perpendicular instead, it’s just not as convenient.
Are aware that you can change the orientation of the sketch axes so that horizontal/vertical are aligned with whatever you want?
Here’s a sketch on the front face of this part where I’ve placed the sketch origin at one corner and aligned the y axis with the sloped face:
As you can see, what is horizontal and vertical are completely under your control.
And we don’t work with 100% rectangular parts. So horizontal and vertical will lost it’s meaning.
Project from another sketch. Parallel and perpendicular. No vert or hori.
Free your mind from earthy constrains.
Always frustrating when I convert from a SolidWorks authored model into Solid Edge. Luckily it is easy to rotate the model and “fix” it.