That's not a good reason. Why not just standardise the entire ecosystem on the same style? If you think that sounds infeasible, consider that Rust, Go and even Python have done this with no problem.
As menctioned, a few years ago Selenium had its methods in camelCase. If your code used Selenium, it had to be camelCase and snake_case mixed. When Selenium standarized, it forced everyone to switch to snake_case.
Nim puts great effort in FFI. It means you can easily use C libraries, using their names, even if the case doesn't match, and your code is still coherent. Look at the sample code in https://www.py4j.org/index.html : why do they end with "random.nextInt(10)" in their Python code? Didn't Python had this solved? Not saying that this is the end of the world, but the Nim way is not a mistake either.