Yeah the 1st one is an Amsoil site with frames and 101 pop ups; should have warned you. Testing the link I also see I should have said you also need to go to the torque converter section under "Informative Articles". The 2nd link should be OK though. Yes; they say disconnect the lines but also suggest you need to be pouring it in at the same rate you are pumping it out. I always understood that their was a risk of damaging the trans using this approach from:
a) Running the trans without sufficient ATF (not keeping up with pump),
b) Overfulling while trying to keep up with what is pumped out causing frothing and pump cavitation and thus similar damage from lack of ATF in clutch pack etc.
I see this Lauarel and Hardy situtaion with two people trying to keep up with the pump output and ATF going everywhere.