wifi-detect.uc is writing a new board.json on every boot

[R.]

This is happening on both of my Cudy WR3000 devices running 25.15.5.
Flash wearing could be a thing. Commenting out the following block stops the writes.

if (!is_equal(prev_board_data, board_data)) {
    let new_file = board_file + ".new";
    unlink(new_file);
    let f = open(new_file, "wx");
    if (!f)
        exit(1);
    f.write(sprintf("%.J\n", board_data));
    f.close();
    rename(new_file, board_file);
}

A quick look at the is_equal function showed no obvious issues. I'll set up a modified wifi-detect.uc to log the before and after contents at boot.
The issue was found with:
sleep 90 && touch -m /etc/timestamp && ubus -S call system reboot
find /overlay/upper -newer /etc/timestamp