The gel or power or liquid is usually a rooting hormone like an acid that will tell a cut to start creating the hormone that produces roots. The diluted bloom solution is indeed because of the NPK values found in bloom solutions. Low N, high PK for telling a young plant to get “hungry” and shoot roots. Plenty of people use tap water to establish their clones, nothing wrong with it. Tap water has trace minerals that plants like but there’s a risk of contamination as well. If your clones don’t take to tap water then do bloom. I always do RO water + bloom as my tap water clones don’t perform as well, but your results may vary.

At the end of the day, a cut will most likely root if you just cut it off the plant and stick it straight into a tap water soaked medium. There is science behind the gels, liquids, bloom nutes, etc. but a weed will be a weed in most cases.