Yes, this is true, and not. Benzos indications is just to make the method more peaceful. But that depends what tutorial you have following.
Based on the drug half life (how long the drug acts), the information indicates two types of benzos. One(Midazolam, short half life) to act quickly and another one(Diazepam, long half life) to have a slow effect. One knocks u out faster and the other keep the unconsciousness(in a coma) for more time, which guarantees more safety for this method.
Midazolam has a more depressant effect on the nervous system, compared to others benzos. Also has a faster sedative effect and a good hypnotic effect(you don't see that coming). Despite this, staying in a coma is the most important thing, which is why a drug is needed to ensure that.
I don't know how many benzos can be indicated to produce a greater depression of the nervous system and keep that, but I believe that two, acting simultaneously, with alcohol, can be enough. You/your body just have to wait for Ami to do his job.