that part was clarified later, "so you need to have fixed function signatures unless you want to have a lot of bother in implementing things"

I should not have used "can't" at that point, correct

To be more clear, you "can't" have a difference between an arbitrary object and a record, unless you know the type of the object and a way to disambiguate that from a record.

Of course, you "can" have a difference, a record "is" `typeof record === 'object' && Object.getPrototypeOf(record) === Object.getPrototypeOf({})` (At least as long as no one uses plain objects as non-recordy things), but, this isn't something I've ever had to care about in any other language. In some you have multiple dispatch built into the language, in some you can just pass named arguments arbitrarily. Javascript and Typescript are very inflexible in this aspect.