All units are defined through several layers of concurrent data intertwined,
in the case of the Kerrigan unit K5, the "hero" flag is defined in the "basic attributes" somewhat
but not defined in the basic flags by default
simply click/toggle the hero field in the "Basic flags"
could/should resolve it (you should get a button on screen and a shortcut from it)
Same for army select
(via un-commandable/army select/etc fields, they all have to make sense as a whole so just test it out...)
(maybe you shouldn't add your hero to it though since you would already have a clunky dedicated button/shortcut above the command card if this first change worked :D )
Again, units from blizz always work, but you have to see all the code layers at once to figure out why it doesn't do "x" or "y" that you think it is supposed to do (usually in validators and such).