> A subset of that is plates which are IR scattering so they don't show up on speed cameras.

Only these are "ghost plates". So called because the letters appear faint, or ghost like, on ANPR cameras.

Using illegal plates, either ghost ones or cloned ones (where they're real plates but for the wrong vehicle) are not loopholes, any more than breaking into someone's house and stealing their stuff is a "loophole" for property ownership.