Your point a) is moot, this is not what this is about. When writing manual SQL nothing stops you from doing `SELECT * FROM persons WHERE age > 'eighteen'` (the `age` field is a number, obviously). Coming from Django I was often bitten by `Person.objects.filter(age__gt=trashhold) # boom!` (note the misspelled variable "threshold") or, if you prefer manual writin SQL: `Person.objects.raw("SELECT * FROM persons WHERE age > {}", trashhold) # boom! as well`. (Admittedly this is unrelated to type safety, just a disadvantage of Python being interpreted, but still something that Haskell/IHP protects me of.)

Regarding b), yes there are good reasons for prepared statements. I won't go into your argument "for scalability" (premature optimization cough) but cached query plans aren't perfect either: data and data typologies change, and so does the optimal query plan. See https://blog.soykaf.com/post/postgresql-elixir-troubles/ for a blog post about Elixir/Phoenix/Ecto users being bitten by that.

> I wonder if the person who wrote this understands SQL to sufficient depth. Not saying either way, just asking.

I did not write the IHP code, just the above comment. But I've read many of CJ Date's books and have a good grasp on the relational model, and of SQL too. I simply don't see things as black/white, there are certain queries where I do prefer prepared statements and functions, or PL/pgSQL even, then there are ones where I use an external .sql file to keep things tidy. But most of the time (especially in the user facing part of a web app) I like my ORMs or SQL DSLs.