Presumably you need to know what an Account and a User are to use that software in the first place. I can't imagine a reasonable person easily understanding a getAccountById function which takes one argument of type UUID, but having trouble understanding a getAccountById function which takes one argument of type AccountId.
What he means is that by introducing a layer of indirection via a new type you hide the physical reality of the implementation (int vs. string).
The physical type matters if you want to log it, save to a file etc.
So now for every such type you add a burden of having to undo that indirection.
At which point "is it worth it?" is a valid question.
You made some (but not all) mistakes impossible but you've also introduced that indirection that hides things and needs to be undone by the programmer.
> There is a UI for memorialising users, but I assured her that the pros simply ran a bit of code in the PHP debugger. There’s a function that takes two parameters: one the ID of the person being memorialised, the other the ID of the person doing the memorialising. I gave her a demo to show her how easy it was....And that’s when I entered Clowntown....I first realised something was wrong when I went back to farting around on Facebook and got prompted to login....So in case you haven’t guessed what I got wrong yet, I managed to get the arguments the wrong way round. Instead of me memorialising my test user, my test user memorialised me.