Behavior of a JK flip-flop

Wiki kinda made a mistake: by the "C changes from 0 to 1 or 1 to 0" it means you can design it to be edge up trigger or edge down trigger not both. If you look at the design it self you will see that the first split from input C only send pulse transitions when you change it from 0 to 1 and when you change it from 1 to 0 it's doing nothing. So this work's alright just a little miss understanding, if you need so here the edge down design I built(just added not before the C):

I fixed this in wiki so this should be fine now.

Btw you can design both edge up and down trigger, you need to send pulse(circled in black) each time the clock is changing. Do it your self as a challenge ☺