RGB/BGR 16 bit treated like RGBA/BGRA?

why PNG color_type == 2 (so RGB triple) in the file

https://github.com/google/wuffs/blob/main/std/png/decode_png.wuffs

} else if this.depth == 16 {
this.dst_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE
this.src_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE
this.filter_distance = 6
choose filter_and_swizzle = [filter_and_swizzle_tricky]
}

is treated like BGRA_NONPREMUL_4X16LE plus swizzle instead of a PIXEL_FORMAT__BGR_16LE?

Best
Paolo