I have wondered the same thing in the past and because it is a "twist tie" thing which is basically a very thin metal wire of unknown variety encased in plastic that can be chewed apart.
I used to just make sure that the back part was kept inaccessible by the birds but I soon found that My female likes to destroy mineral blocks just because she can. Within a few hrs she can expose the wire on the In-Side of the cage and starts trying to work at the wire attached to the bars. For this reason, I decided that mineral blocks with the ties are not safe with my bird.
I do provide a cuttle bone and have used other types of mineral perches that do not have the little wire ties, which tend to last a little while longer.
I hope this helps some. Perhaps one of our more educated members will be along shortly with their input.