no it cant. overall tire diameter determines how low the truck can go, not just the rim size.
for example. a 15 inch rim with a 275/60 on it is about 28" tall. a 20 inch rim with a 255/40 is also about 28" tall. rim does not matter, overall tire height matters which is determined on what tire he runs.
just because he wants the look of 15 inch rims with a nice side wall does not mean the truck cant lay out on “big rims”