The wording looks reasonable but it doesn't seem to add much that is not
already said:

'''
class SystemRandom( [seed]) 

Class that uses the os.urandom() function for generating random numbers
from sources provided by the operating system. Not available on all
systems. Does not rely on software state and sequences are not
reproducible. Accordingly, the seed() and jumpahead() methods have no
effect and are ignored. The getstate() and setstate() methods raise
NotImplementedError if called. 
'''

I hesitate to include anything about cryptographic strength because that
isn't really guaranteed on any system.  At best, there are a fixed
number of bytes of machine generated entropy.  At worst, it is
deterministic (computed from time, etc) or it is not available at all.