Water temp and gas gauge not accurate while engine running.

Yes, the reason you need to tie the "IGN1" (ignition run, dark blue), and the IGN2 (bypass, brown) is that most mopars the "run" circuit GOES DEAD in start.

What you are checking in with key in "run" / engine off is for bad connections through that circuit path, although the MSD "trigger wire" relieves a lot of the load. You still have the field and regulator, and on some cars, some smog junk, and such as sixpacks and a few others, distributor retard solenoid, electric choke if used, and carburetor idle solenoid.