[opcvx]

You missed the relevant text:

>or equivalent; 10)

>10) Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as char * * argv, and so on.

And Standard also says that:

>or in some other implementation-defined manner.

and:

>In a freestanding environment (in which C program execution may take place without any benefit of an operating system), the name and type of the function called at program startup are implementation-defined.

So main can be pretty much anything according to the Standard, depending on the system.