Re: range cal.
Absoutely. Lets look at the big picture. To start with, we are only calculating the most probable demand on the service or main feeder and not the individual branch circuits to each of these cooking appliances. So imagine we have a tri-plex each with a 19.2 KW range. What is the likely-hood that all three will be used at exactly the same time at their full load? Very little. (I would doubt that not even one range would ever be loaded to 19.2 KW, meaning all 4 burners on high and the oven at full heat.) Even so, what are the chances that all three dwelling units will indivdually be using the full calculated load of their portion of the service. Very little again.
It is even more likely that none of three individual dwelling units will be loaded at their calculated demand, therefore the NEC provides these great reductions in sizing the service.