Xcode – Swift VolumeUnit conversation from quarts to cups seems off

I’m working on some Swift code that is intended to supply multipliers for conversions between some common volume units. Unless I’m using it incorrectly, I seems to have found an anomaly in conversions from quarts to cups.

Here’s a simple unit test I wrote to demonstrate the problem I’m running into:

    func testUnitConversions() throws {
        let quarts = Measurement(value: 1, unit: UnitVolume.quarts)
        let conversion = quarts.converted(to: UnitVolume.cups)
        let value = conversion.value
        XCTAssertEqual(value, 4)
    }

In Xcode 15.3 it fails with: "testUnitConversions(): XCTAssertEqual failed: ("3.9431375") is not equal to ("4.0")"

Every conversion site I look at on the web tells me that a quart equals 4 cups. Am I doing this conversion incorrectly or is it a Swift issue?