Hi Mike
Hope you are doing well.
Built-in validation does not only running on the client-side, depends on your setting and application type it's also running on the server-side.
You said "end user does not have the possibility to change values", but it's only a normal use case,
Because the input is on the client-side(browser), so there are many methods to change the input value.
So it's nice to use validation in this case.
Kind regards,