Sure. However the any type lets the nulls in. And the any type is very convenient, perhaps even necessary to use in some situations. So then you are back to plain old js check blocks and ternaries littered everywhere. If you miss one, well, I don't need to remind anyone of the ubiquitous js console error which every js developer has burned into the back of her/his brain.

I use the no-explicit-any Typescript ESLint check and tsconfig no-implicit-any, never turn them off unless absolutely necessary, making this is a non-issue. Not that I’m not interested in Reason for other reasons though!

That's fine if you can control this configuration I suppose. But the escape hatch is there, so in my opinion TS doesn't go far enough.

Note that "by default" here means "when strict mode is on, which is explicitly turned on when you run tsc --init". If you don't specify a config value for strict mode, it will be off. (At least last time I checked.)