The thing with these wise philosophies of caution, of which "runway behind" is one of many, is that you have to spot when they become ludicrous.
In my early PPL days our school was at Manchester and we shared the runway with the big boys. The earliest intersection from the south side to 24 (only the one runway in those days) was some 500 metres from the threshold. This left my Piper Tomahawk with a mere 2500 metres to get airborne.
I dread to think how a "Request backtrack" would have been received by ATC.