> You'd be a moron to pass an argument of a different type 'a couple of hours' into the training

Huh?! At least in non-ML code this happens all the time, data fetched by whatever thinggie that uses zillion chained libraries of code nobody has time to audit, comes in hours or days late in a long running service blowing it up... eg. "oops, point.x is now no longer and integer but more like a map[ErrorObject->vector[int]]" bc something blew up in a very unexpected way in some other nodejs code light years away from the business logic you hold in your head... (yeah, the service gets restarted, but at some point some data that should have been saved in the DB hasn't been am may need to be recovered manually from some obscure log if even recoverable)