My 14k btu Mr.Slims' manual gave amounts of freon to be added for X amount over 25 but no mention of subtracting for less than 25'.
Maybe the size difference?
I think its just an aspect of their machine. The 12k model manual does not require subtracts for less than 25'. But some brands do in fact require it. The Freidrich breeze come with a 25' charged line set. Its fixed to the head. Those seem very easy to install - but they are a two man job also imho.