A couple of points here:
The example from the OP is good film with a bad process. It has severe crossover and some other problems to boot, and he does not recognize it which is even worse. This may be due to his technique or due to the process temperature which is low. Also, black plastic garbage bags leak light big time. Look through one! Nuff said on that!
Don't use this guys advice.
Use 100F, use a real changing bag, use a prewet to temper the tank, and use a bleach then fix to insure that all silver is removed.