I think the point he was making is that, if you are looking at travelling, litres/K or litres/nm is the most relevant measure. You can be burning 100l/hr, but, if you go 100 km in that hour, it is very good economy. 100l/hr @ 20knts/40km/hr, is, on the other hand , appalling.Litres per hour is also a useful quantity, you may prefer litres per K, and thats fine, but it is not the only measure of fuel use.