The idea that someone is good at another language so they'll automatically be good at another is a common misconception. In fact, they're likely to be worse because they're less likely to spend time trying to learn things from the ground up and less likely to write idiomatic code.
It's especially bad with js/ts because of it's popularity (so lots of new programmers that complain about how NaN doesn't equal itself), and because it's the defacto web language so lots of people are forced to use it as a secondary language that don't want to spend time learning it.
