DOS isn't a "shut down" OS. Just flip the switch.

So this is completely unnecessary?

1Calling int28 so MSCLIENT can flush...
2Resetting DOS filesystem and BIOS disk handler... done.
3Giving disk handlers some time... Spinning down..... Disks stopped.

As already said, in DOS there's no real need to use the shutdown command.
Just common sense. In order to shut down a DOS computer, make sure
a) the HDD activity led stays off for several seconds, indicating that no program is writing to disk
b) that on really old machines, the "park" command is executed, so ancient HDDs without auto-park feature go to sleep savely

As always, there are exceptions to this. Like if using network/server software, caches like smartdrive or a data-logging application.
But in principle, DOS is a read-only operating system. During boot-up and while beeing idle, it does not
attemp to write any data to the disk. Also in pure DOS, the filesystem doesn't have to mark itself "dirty" or "clean".
That's win95+. 😉

Thank you for explaining. The oldest OS that I used in my life was Windows 95, so I was afraid of shutting down by just cutting power off, but looks like it is the right way for DOS.

I always liked shutdown DOS utilities for ATX powered machines.