provenance/4 matches the site

public static Activity Trading_Shares()
{
    var trade = new Activity()
        .WithContext()
        .WithId("https://linked.art/example/provenance/4")
        .WithLabel("Trading Shares of Painting between Two Dealers")
        .WithClassifiedAs(Aat.ProvenanceActivity);

    trade.Part = [
        new RightAcquisition
        {
            Establishes = [Share("40% Ownership by Dealer 1", 40, "Dealer 1").WithAppliesTo(Painting)],
            Invalidates = [new Right().WithLabel("30% Ownership by Dealer 1").WithClassifiedAs(OwnershipRight)]
        },
        new RightAcquisition
        {
            // The site's example gives Dealer 2's new 60% share a value of 70.
            Establishes = [Share("60% Ownership by Dealer 2", 70, "Dealer 2")],
            Invalidates = [new Right().WithLabel("70% Ownership by Dealer 2").WithClassifiedAs(OwnershipRight)]
        }
    ];

    return trade;
}

var activity = new Activity
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/provenance/4",
    Label = "Trading Shares of Painting between Two Dealers",
    ClassifiedAs = [Aat.ProvenanceActivity],
    Part =
    [
        new RightAcquisition
        {
            Establishes =
            [
                new Right
                {
                    Label = "40% Ownership by Dealer 1",
                    ClassifiedAs = [Aat.Term("300055603", "Ownership Right")],
                    PossessedBy =
                    [
                        new Group
                        {
                            Label = "Dealer 1",
                        },
                    ],
                    AppliesTo =
                    [
                        new HumanMadeObject
                        {
                            Label = "Painting",
                            ClassifiedAs =
                            [
                                new Type("http://vocab.getty.edu/aat/300033618", "Painting")
                                {
                                    ClassifiedAs = [Aat.TypeOfWork],
                                },
                            ],
                        },
                    ],
                    Dimension =
                    [
                        new Dimension
                        {
                            Value = 40,
                            Unit = new MeasurementUnit("http://qudt.org/3.0.0/vocab/unit/Percent", "Percent"),
                        },
                    ],
                },
            ],
            Invalidates =
            [
                new Right
                {
                    Label = "30% Ownership by Dealer 1",
                    ClassifiedAs = [Aat.Term("300055603", "Ownership Right")],
                },
            ],
        },
        new RightAcquisition
        {
            Establishes =
            [
                new Right
                {
                    Label = "60% Ownership by Dealer 2",
                    ClassifiedAs = [Aat.Term("300055603", "Ownership Right")],
                    PossessedBy =
                    [
                        new Group
                        {
                            Label = "Dealer 2",
                        },
                    ],
                    Dimension =
                    [
                        new Dimension
                        {
                            Value = 70,
                            Unit = new MeasurementUnit("http://qudt.org/3.0.0/vocab/unit/Percent", "Percent"),
                        },
                    ],
                },
            ],
            Invalidates =
            [
                new Right
                {
                    Label = "70% Ownership by Dealer 2",
                    ClassifiedAs = [Aat.Term("300055603", "Ownership Right")],
                },
            ],
        },
    ],
};

Generated from the object the example builds: every property that is set, as object initialisers, with the vocabulary constants where a term is in the registry. The fluent helpers are a convenience, not a requirement; this form and the one as written produce the same JSON.