> My worries about coding all these things into type systems is that this freezes the semantics at a time during development where one is still figuring out the ideal semantics.

I don't get this part at all, especially in a language with static typing. It's completely normal for me to not be sure which type I need here and so I use a type alias, or if I'm even less sure I make a wrapper type so that it only has the properties I choose. So I don't see this "freezing" semantics any more than an identifier name would - we can just change it if we change our minds, no problem.

To give a comparable example from elsewhere, when I'm still feeling out the problem I often write Rust's loop, the infinite loop which is Rust's only primitive looping structure (for and so are just sugar). That doesn't mean I write only weird odd-ball loops, but when I'm not sure the raw infinite loop is fine if I decided to consume all the Widgets in this Vec<Widget> like a for-loop but it's also OK if I decided to index through it, or do something entirely different. Rust's "clippy" will prompt me to write a more idiomatic while-let or for-each loop when I've nailed down the whole thing.