question on model attribute

[schaefer01]

hi,
I'm going through the examples on the main url for this github and found two similar but different examples:

machine = Machine(lump, states=['solid', 'liquid', 'gas'],  model_attribute='matter_state', initial='solid') 

machine = Machine(model=lump, states=['solid', 'liquid', 'gas', 'plasma'], initial='solid')

the difference is that first responds to:
lump.matter_state
and the second responds to:
lump.state

I'm curious as to the purpose, which on first glance might be towards refining naming conventions to add explanatory
detail in writing code but If there is a different/additonal purpose, I'd like to know what it is.

thank you