Doing it as above means only one fusible link is needed.
It also lets you monitor the battery charging and discharging.

Connecting the Alternator output direct to the battery or tying in at the starter relay does the same thing.
It gives the sometimes high charging current a seperate route to the battery, reducing the load on the main feed wire and connections.
Difference is that a fusible link is needed in the connecting line to protect against battery grounding, and the ammeter will no longer show charging.