It may be a real order, but it’s a very specific one used as part of Squadron Parades, when marching in column of threes, with multiple flights. (Something I have never done in 16 years!)
I don’t know about you, but I’m not routinely teaching that subject on parade nights, nor do I specifically see a need to ever do so, therefore, if I was to be doing it on an ad-hoc basis, throwing in the word ‘immediate’ shouldn’t really be giving you an aneurism.