Over the years there have been more fluorocarbon ukulele strings vs. fishing line (leaders) than I can count.
When less than a yard of strings lasts a couple of years, and is spread over a dozen brands, no unique formulary string can be manufactured in lower quantities to make it economically feasible.
That said, I don’t think people, outside the industry, have the knowledge to figure out the various properties of all the different fluorocarbon line that is available. Nor do most people want to make the investment in trying out dozens of fishing line brands and sizes. Especially if you only have a couple of ukes.
I’ve been using Seaguar exclusively for many years. But I have a number of ukuleles and my tenors are tuned from Bb to C, so being able to mix-n-match to get the right balance is worth it to me. Even so, I have not yet been able to bring myself to try the Gold Label, much less try some other brand.
If you like the ukulele strings you are using, it is probably not worth it to use fishing line. If you find yourself tossing a lot of strings, or need to mix sets to dial in a tone, it might be a good route.
John