Kind of, but even an average runner can experience a bug or refine a strategy through repeat practice, which they often share with the community through streamed runs or discords.
You tend to have certain people who are more interested in glitch finding and spend most of their focus on that over actually running the game. Then you have TAS runners (often overlap with glitch hunters) who make TAS-only runs to determine what the absolute limit is in a game. Finally, you have the remaining 95% of the community, runners grinding the game over and over.
Strategies from TAS often are repurposed by speedrunners, perhaps most famously in Mario 1 any%, where several strats used by top runners were once considered infeasible for humans.