I have mixed feelings about this.
Knife crime is a growing problem, and we should in theory welcome measures that assist in controlling such crime.
On the other hand, when I was working in London as a maintenance engineer I often carried around knives or other bladed articles as part of a tool kit. Carried either from one work place to another, or to/from home.
I believe that carrying such articles was legal as use in my employment was a "reasonable excuse" for having a knife or bladed article in a public place.
I carefully avoided Liverpool street underground station when a knife arch was in use at that place, making use of a bus, a taxi, or walking so as to avoid the knife arch.
Whilst I believe that I was not breaking the law, I was reluctant to take the risk that a police officer might take a different view.
Being arrested for "carrying a knife" would have been most troublesome, even if later acquitted in court. A court case could entail significant loss of earnings, and possibly legal expenses also.
Being acquitted is little consolation if one has in effect been "fined" two days pay, and spent a few hundred pounds on legal advice. Enough such acquittals could have ruined me.
Having seen pictures of the sorts of knives these people carry I suspect it would take only a little bit of ingenuity to tell the difference. Also there is a difference between carrying a knife on your person - that is a manner that is to hand and ready for use - and in a tool box or the like. A chef might reasonably have a reason to carry cooking knives in an appropriate container for example.