I generally ask the question "why" as well.
I generally feel urine would vary in analysis also. Especially from person to person.
Although.....
Here's an interesting video I saw several weeks ago. There's good comparison footage too.
Apparently it's best used fresh, straight away as well.
Beautiful plants too.
I personally piss on my grass, or a big ol' tree, if I couldn't be fucked finding a toilet.
But otherwise what's the point?
"The exact breakdown of urine varies depending on the diet of the pee-maker. The more protein a person consumes, the more nitrogen will be excreted into the urine. Typical Western Diet pee has an NPK ratio of about 11-1-2. In comparison, blood meal is 12-2-1 and cottonseed meal is 7-2-2."
Far from an ideal single source. Especially in flower.