chiseled brickstone is replaced by smooth andesite in a igloos underground room

I found an igloo and I went to the underground room of It. When I destroyed the to red carpets, I saw that there is a smooth andesite underneath it. According to the pattern of the basements floor, this shuold have to be chiseled brickstone. On https://minecraft.gamepedia.com/Igloo I found the smooth andesite also in the pictures of the igloos design