An OC of mine used to refer to single file as 'idiot file'.

However, is a single file always necessarily an idiot file? Is it not a matter of balancing pros against cons? I assume (please correct me if this is wrong or simplistic) that a reason for it in Astan was to follow narrow routes, where IEDs were (perceived as) the main threats. Kinda like a cleared route through a minefield.

Terrain can be another reason for using the idiot file, if narrow channels of undulation or vegetation in otherwise flat or open ground provide the only cover or concealment. A double edged knife of course, given that these channels are ideal places for IEDs.

Another reason for single file could be control during night movement, think Falklands with its battalion snakes.

I suppose what I'm getting at is that emotive labelling of tactics or methods that - under the right context - can be quite valid, may lead to unjustified exclusion of those methods. (Junior) commanders can be quite sensitive to emotive labels. Saying 'the use of single file needs to be carefully tested against its tactical disadvantages' is not the same as saying 'use the idiot file at your peril.' 'Afghan snake' is of course not as emotive as 'idiot file', and may well have the context built in.

I'm not bringing this up to pin-pick on this particular example for its own sake, but as a training observation I made years ago. My section commander under afore mentioned OC did all he could to avoid using single files during one exercise, sometimes to the point of ridiculous. It opened my eyes to other such examples where labelling can have an adverse effect on training. However, I'm still interested to see if my assumption as to why single file was so prevalent in Astan is correct.