Why does the relation go through Boyce-Codd normal form?

Question

Database

There is a table consisting of the following fields: restaurant, type of pizza, delivery area
It is assumed that all three fields are the primary key.
This wikipedia example is offered to demonstrate normalization to 4 normal form. This means that this relation goes through Boyce-Codd normal form, but I can't understand why...
After all, there are functional dependencies (restaurant -> type of pizza) and (restaurant -> delivery area) in the relation, the left side of which is not potential key...
In the example, these functional dependencies are described as multi-valued, that is, the type of pizza multi-valuedly depends on the restaurant, as well as the delivery area from the restaurant, since they have a common determinant. But shouldn't they have already been resolved at the level of the Boyce-Code form, since this general determinant is not a potential key?
Or does the fact that all three fields are the primary key change something? But what?
Thanks in advance for the replies. I would like specifics, since there is a desire to deal with normal forms once and for all.
I apologize if I didn't describe the question in enough detail. If something is not clear to you, you can refer to the source and read this example there:
https://ru.wikipedia.org/wiki/%D0%A7%D0%B5%D1%82%D...

Answer 1

yes, there is something
to say in order to answer the question, you need to get into your head and figure out what you know, what you don’t know, what you understood, what you didn’t understand, and what you understood wrong and why it happened that you didn’t understand or understood wrong
if so in the school teacher will be with each student - he will retire earlier,
therefore, in order to assimilate the material, they came up with PRACTICE
in your Wikipedia link, everything is described quite clearly
, but described by practitioners for a long time and taking it for granted
in practice, in general, 3rd is used almost always, maximum BC
only, maybe, in transactional systems, maximum normalization is ensured by functions and not by initial design: because in the course of business, data and structure CHANGE
therefore, having practice, you either SUDDENLY begin to understand your question yourself, or understand its stupidity