It's not just a question about style. ?int can be enforced at compile-time while the null and type check would be caught at runtime.
Edit: And my point here is basically that less experienced programmers will get it, which makes the barrier to entry lower. Going back to my previous statement, without a better reason, I'd encourage self documenting code and less abstract approaches. This is a pretty mild one, easily looked up...and probably a great thing for people to learn, but still more complex at the end of the day. Language is almost irrelevant here, it's a general statement.
Going further, to even figure out why you need to do all this, that human would need to know such concepts as variables, data types, and nullability. The notion that variables can have designated types is a pretty obvious takeaway from the first two.
Finding the definition of "!==" is easy, simply searching that [including quotes] gives me the answer. Looking for something like "?int =" just gives me useless responses upon first glance.