I think in this case, they're attempting to keep the "inked" look where lines start and stop. Pixel doubling would result in aliasing (or, rather, a "pixelated"

I think in this case, they're attempting to keep the "inked" look where lines start and stop. Pixel doubling would result in aliasing (or, rather, a "pixelated" look) and bilinear filtering results in a "blurred" effect. The intended effect with this goal being to give the appearance that the anime was produced in 4K.