Missed layout optimisation with multiple niches

I tried this code:

use std::num::NonZeroU8;

struct Test {
    niche_one: NonZeroU8,
    niche_two: NonZeroU8,
}

fn main() {
    assert_eq!(
        std::mem::size_of::<Test>(),
        std::mem::size_of::<Option<Option<Test>>>()
    );
}

I expected this program to exit fine, and fit the tag of the second option in the available niche.
Instead, the program panics, as the second option wastes a byte of memory making it's own tag byte.

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rustc --version --verbose:

rustc 1.77.0-nightly (e51e98dde 2023-12-31)
binary: rustc
commit-hash: e51e98dde6a60637b6a71b8105245b629ac3fe77
commit-date: 2023-12-31
host: x86_64-unknown-linux-gnu
release: 1.77.0-nightly
LLVM version: 17.0.6

Start by reproducing the provided Rust program with the reported rustc nightly version and compare its layout across relevant compiler versions. Investigate rustc's type-layout and niche-optimization handling for nested Options with multiple NonZeroU8 fields. Done means the reported layout behavior is corrected or the issue is explained and covered by an appropriate compiler regression test.