You added longer wire plus three or four wire connections plus the resistance on the toggle switch contacts.
The purpose of the wire from the #2 spade terminal of the voltage regulator in the alt is to tell the voltage regulator what the voltage is at the battery. There is very little current flowing in this wire and with low resistance, there is little if any voltage drop. This allows the regulator to get an accurate picture of the battery condition.
The wire from the BAT terminal to the battery has high current and even with larger wire will have a voltage drop. More so under heavy load (lights, stereo, AC, etc.,).
Running a wire directly from the #2 terminal to the BAT terminal prevents the voltage reg from seeing what the actual needs of the battery are. It can monitor the alt output, but not the battery needs.
If you look around this forum, you will see people wiring the #2 to the BAT and telling all others to do the same. It will charge the battery. It just won't do as good a job as Delco designed these alternators to do.