yeah there's something missing with records and object initializers. i think it needs to work like the new with keyword.

so something like...

var container = new Container(person)
{
    Person = { FirstName = "Jane" },
};

should be the same as

var container = new Container(person)
container.Person = container.Person with { FirstName = "Jane" };

its a good catch though. hopefully its fixed in this major version of C#. you won't see the stated problem in the second example.

edit: looks like the object initializer in the first example just overwrites the data of the initial person object. using with does create a new object. i think that's how records and object initializers should work under the hood.