So just because it's common in fiction, doesn't mean Hyssop's attack is not absolute zero. That's not a valid counter, and till now I personally don't think anything shown in series refutes it being actually AZ. It's not like the name of attack is "AZ". The name of attack is actually "Ice Lance". AZ temperature was stated while explaining how the attack works.
- They have a character, who is sitting there for the sole purpose of giving explanations and back-stories about his fighters(all kaioshins and hakaishins are currently doing the same thing), explaining how the attack works.
- They also added this information on their official website.
It's clear they want to convey this point and that too blatantly. This is the same as being FTL, we don't see actual feat happeneing all the time, nobody states the velocity everytime, we don't see the side-effects everytime, we only have some statements and confirmations like these.