Svelte is a bad example. They have roughly identical type checking before and after that switch. The switch is mostly just an aesthetic preference for one syntax over another and an ideological stance about being able to run code directly in a browser without a build step.

It's not an "aesthetic preference"; it's a functional preference for debugging and iteration speed as cited by the team.

Which is quite hypocritical coming from a compiling framework and thus such a ridiculous stance.

We hate build steps in our build step.