I can (I'm the author). The partitions are aligned to 2048 sectors (4096 is evenly divisible by 2048). But also note the first usable sector is 2048, not 0 - so the first partition, although we tell sgdisk to start at 0, actually is from sector 2048-4095. I don't know the exact reason why the first usable sector is 2048 - I believe it has to do with legacy support and MBR compatibility - but I'm not sure of the details.
