I've noticed that in both P6 and MSP, values for Units (Work) are generated by assigning a Resource.
It's also possible to it is possible to directly enter a value for Units (Work) without assigning a Resource.
The latter method seems to behave much better when extending/shortening planned durations.
Both methods contribute to the 'cumulative units' outputs that are possible with P6 and MSP.
Is there any reason why I would want to generate my Units by assigning a resource, if I don't plan on doing any resource levelling on this particular schedule?