How can evil doers be 'reborn' as 'human'?
might be lost in translation somehow.   from this 


  "No ce kāyassa bhedā paraṃ maraṇā apāyaṃ duggatiṃ vinipātaṃ nirayaṃ
  upapajjati, sace manussattaṃ ..


if replace "in stead of" with "if not" , that it makes more sense.  


  if not reappearing in the plane of deprivation, the bad destination,
  the lower realms, hell — he/she comes to the human state,....


It could also mean that when karma is exhausted in suffering plane, and being appear in human world after? So once you burn your "debt" you move to the next phase or rebirth, lacking the "debt"  

The vice versa is said to occur at the end of a rebirth in the heavens as a god. They burn through their "good debt" quickly and tend to fall into the lower realms when their dues are paid. 

I am an amateur self taught Pali.  I could be wrong but at least it opens up for those who know more about Pali to chime in.  Could "No ce" together with rest of a sentence,  is better to translate to "if not" rather than "instead of"?