`clap_usage` generate invalid KDL document with `Option<bool>`

[koitococo]

I use clap to build my cli app, and clap_usage to generate a KDL document for completions. Below is a minimum reproduction:

#[derive(clap::Parser)]
struct Args {
    #[clap(short = 'b')]
    this_is_a_bool: Option<bool>,
}

fn main() {
    use clap::CommandFactory as _;
    clap_usage::generate(&mut Args::command(), "demo", &mut std::io::stdout());
}

which produces:

name demo
bin demo
usage "Usage: demo [OPTIONS]"
flag -b {
    arg <THIS_IS_A_BOOL> {
        choices true false
    }
}

When invoking usage complete-word --shell fish -s "$(cargo run)", usage complains:

  × Failed to parse KDL document

Error: 
  × Expected identifier string
   ╭─[6:17]
 5 │     arg <THIS_IS_A_BOOL> {
 6 │         choices true false
   ·                 ──┬─
   ·                   ╰── not identifier string
 7 │     }
   ╰────

Error: 
  × Expected identifier string
   ╭─[6:22]
 5 │     arg <THIS_IS_A_BOOL> {
 6 │         choices true false
   ·                      ──┬──
   ·                        ╰── not identifier string
 7 │     }
   ╰────

clap and clap_usage is the latest version:

[dependencies]
clap = "4.5.46"
clap_usage = "2.0.3"

It only happens to Option<bool>. If replace it with bool or Option<SomeValueEnums>, everything seems ok.

[koitococo]

It appears to be a known issue: kdl-org/kdl-rs#132. Is there any workaround we can do?