Yeah, my thought was it was someone unfamiliar with mobile measurements. It's meant to handle mobile UIs, which means "pixel" doesn't exist as measurement because screens are different densities, different aspect ratio. You could do a thing like make an empty block with full padding to the left or right, or just center align it.
I made a mobile game in Ren'Py and it was hard for me because of the fixed assumption that something was 800x600 and such and you'd add padding on the sides lol. Unfortunately with mobile, everything is relative to each other. iOS was a little easier back when it was one size, but now it's not.
It's still a lot easier to do than fixing sizes on CSS, flexbox, etc because you'd be able to have fine control over these things.