The docs look correct to me.  For example,

>>> from datetime import *
>>> td = datetime.now() - datetime(1,1,1)
>>> td
datetime.timedelta(735103, 61756, 484000)
>>> td.total_seconds()
63512960956.484
                                                                ^
What the docs say match that output:

>>> (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10**6) / 1e6
63512960956.484

Your suggestion's output:

>>> (td.microseconds / 1e6 + (td.seconds + td.days * 24 * 3600) * 10**6)
6.3512960956e+16

You're multiplying the number seconds by a million - not a good idea ;-)