Antoine, if I understand you correctly, you are saying that any type that defines __index__ is an integer, and should therefore also define __int__, in which case Python can just use __int__ and not worry about __index__?
Here's the problem with that:
--> '%x' % 3.14
'3'
While I am beginning to agree that an integer type needs to implement both __int__ and __index__, it still remains true that Python needs to call __index__ if what it needs is already a real, true int, and not just something that can be truncated or otherwise converted into an int -- such as float.