When the alternator is producing enough power at 14 Volts, then that's the power source.
The advantage of tying in close to or after the battery is:
a. times when the battery is the power source
b. equipment that may be sensitive to the electrical noise from the alternator.
I'm not the one to explain how a battery can dampen out some of that noise but accept it as realty.
With EFI and an AMP, your strategy is probably a good one.
Just make sure the alternator output line can carry the currents for that stuff and maximum battery charging without much resistance.
