Most crime I'd suspect is done with what is too hand - it doesn't tend to be pre-mediated that someone purchases , waits for the appropriate time or incident then unfurls their " special " knife to go and do damage to some soul.
I'd imagine the most used knife in blade attacks is something small and pocketable , not anything the size of your arm that needs to be kept outside and overtly signalling ones intentions to do harm with it.
I've done a lot of studying via my interests and activities in Combatives relating to knife crime and I could easily point people to some horrifying footage and outcomes of knife attacks.
I suspect most people purchasing these Zombie knives are people who just want to own it an fondle it in their bedrooms - most likely pre-pubescent boys.
The most used knife style in any attack I'd guess is probably a small kitchen knife when one partner 'flips' in a domestic scenario and attacks the other.
I'm not outwardly defending anyone's right to own a Zombie knife - I certainly don't wish to possess one , but I would where the enforcement of the law is concerned be wary of mission creep in terms of what is now seen as acceptable vs unacceptable and then thus banned.
This echos to me of the similarity in Gun crime in the UK and the reactionary response to it - Most guns used in gun crime are not recorded firearms but have been smuggled in and so ' off the books' but the reactionary legal response is to make it harder and harder for those firearms owners who follow all legal requirements to own firearms. Punish the collective for the crimes of a few.
And yet the wonderment is why Gun crimes still continue..