From what I see and understand , the alternator has two grounds, one is the ground connection through the brown cable that connects to the voltage control module, apart from being obviously bolted to the engine, which has its own ground connection through the flat ground cable on the part of the engine boot engine and firewall.
But if your question is, if the alternator has a direct (chassis) ground connection apart from the above, I would say no.
In the images that I show you, I connect the ground pole of the battery to the pole of the fat red cable that reaches the alternator, but I have not tested from the battery pole to the alternator casing, but you do not think, that when in contact the Alternator pole to casing should give the same resistance reading (Ohms)?