Niches aren't special, they're not a calling that you will do for the rest of your life. Niches are marketing. A niche is how you communicate to other people what you have credibility in. You won't be stuck in it and even if you only want to be in that niche you will explore nuances. Fractals and recursions.
Even when someone has a niche, they backfill it. Read any biography and they're connecting the dots in the past.
This is actually how the human mind works. Experiments with severed brain hemispheres show that the brain will make up a memory to explain something it hasn't encountered. Your brain will make up a story so that causality can be explained.
Literal blind spots also work this way. Your retina blocks part of your sight but your brain backfills. You're not even aware that this is happening.
Why subject yourself to a niche? Instead, use a niche as a tool.
Backfilling your niche isn't cheating or unnecessary. The act of choosing a niche and then maximizing it is unnatural.