Why does `Quartiles::values()` return `[f32; 5]` instead of `[f64; 5]`?

[your-diary]

Internally, each field of Quartiles struct is of the type f64:

pub struct Quartiles {
    lower_fence: f64,
    lower: f64,
    median: f64,
    upper: f64,
    upper_fence: f64,
}

But values() returns them after manually casting them to f32:

pub fn values(&self) -> [f32; 5] {
    [
        self.lower_fence as f32,
        self.lower as f32,
        self.median as f32,
        self.upper as f32,
        self.upper_fence as f32,
    ]
}

What is the design decision behind this?

related: #496 (comment)