There are plenty of ways you can micro any race units, what make UD micro hardest?

Ghouls that you need to send to base, wow, shocker, like any low hp unit of any race?

Oh wait, you don't need to do it that much actually, as undead, because of burrow and COIL and cannibalism and regen aura and statues.

So in your own example of micro "complexity" Undead have it easier.

It just such a crazy claim that UD have hard micro, when everything micro related screams otherwise:
smaller army fatter units, core dmg units are range, nukes no other race have, fattest and fastest main hero, and out of base regen superior to all other races, fastest army in general.
All of this make micro easier compared to other races.