Bug with clipboard.writeText() or am I missing something?

Question

I am trying to paste into the Gmail Compose field where you input your email's body, and all that. So, here is the issue: I want to paste parsedBody in, but for some reason, the lines.slice(2).join('\n').trim(); is not being applied to the pasted text. However, what's being logged to the console in console.log(parsedBody); has the slicing and joining applied.

So, is this a bug with the navigator.clipboard.writeText API, or am I making a mistake here?

const responseContainer = document.getElementById('generated-response');
if (responseContainer.value.length === 0 || generatingResponse) return;
const view = composeView.getBodyElement();
view.innerHTML = `<div>${responseContainer.value.replace(/\n/g, '<br>')} ${view.innerHTML}</div>`;
mainView.close();
try {
    const fullEmail = responseContainer.value;
    const lines = fullEmail.split(/\r?\n|\r/);
    const subjectPrefix = "Subject: ";
    let parsedSubject = "";
    if (lines[0].startsWith(subjectPrefix)) {
        parsedSubject = lines[0].substring(subjectPrefix.length);
    }
    composeView.setSubject(parsedSubject);
    const parsedBody = lines.slice(2).join('\n').trim();
    console.log(parsedBody);
    await navigator.clipboard.writeText(parsedBody);
} catch (error) {
    console.log('Failed to copy to clipboard');
    console.log(error);
}

I tried pasting in the parsedBody, and logging it too. What's being logged is completely different from the parasedBody being pasted.