Jaggies with drawLine

This code

local gfx <const> = playdate.graphics
local gmt <const> = playdate.geometry

local orgWidth = gfx.getLineWidth()

function playdate.update()
    gfx.drawLine(gmt.lineSegment.new(15, 15, 1, 1))
    gfx.drawLine(gmt.lineSegment.new(15, 1, 1, 15))
    gfx.drawLine(gmt.lineSegment.new(35, 15, 21, 1))
    gfx.drawLine(gmt.lineSegment.new(35, 1, 21, 15))

produces this output:

The X on the left is with the standard linewidth of 1. To me it looks more like a width of 2, but that is what it is. I would like my lines to look more like the ones on the right. But in order to do that I need to set the linewidth to something below 0.5.

Is there some way to fix this? The upper right pixel of the right line going up and to right is not quite at the coordinate set in the lineSegment. (34, 1) instead of (35, 1).
I'm guessing that it has something to do with the fact that I set the width to below half of the original. It also looks like only the left half of the pixels of each line is drawn.