Nozzle Tip Relationship to Hose Diameter Rule

The nozzle tip may not be more than 1/2 the diameter of the hoseline. This is an old rule of thumb I have heard many times. I have looked through 3 of my books today and cannot find the rationale that explains this. I am assuming it has something to do with the amount of backpressure and formation of the stream, but I am looking for the formal/hydraulic explanation. Also, I am questioning if velocity has something to do with this, but I am having trouble putting it all together. Help?

Friction loss vs tip size

1.5" = .75 or 3/4" 37.5 FL .875 or 7/8" Effective 54.0 FL

1.75"= .875 or 7/8" 34.8 FL .975 or 15/16" Effective 53.0 FL

2.0" = 1.0 or 1" 32 FL 1.125 or 1 1/8" Effective 50.0 FL

2.5" = 1.25 or 1 1/4" 21.1 FL 1.125 or 1 1/8" 14.0 FL

These are all calculated friction loss per 100' foot for each size of common hose. I did not include 3" as I don't feel it should be included as an attack hose. Just something to think about as there is not a direct linear relationship as you jump up in size between hose and tips size but it is pretty close until you get to 2.5". I also included the next tip size up as discussed previously. I included 1 1/8" as it is commonly used for 2.5" hose. Food for thought.