That’s because the default figure size is 800x600, so halving that is going to produce something around 400x600 which is rather tall.
You can either let the figure size determine the plot sizes and do Figure(resolution = (800, 400)) or something to that effect.
Or you can predetermine the axis sizes, and then adjust the figure size to fit using resize_to_layout!() as described on the bottom of this page Aspect ratio and size control tutorial