Duplicate Window Launched on 3rd Click

Still working on the addon, and for ease of use, I am separating one configuration item into a separate popup page.

So I have a button that opens the popup.

The first time, the window/tab (depending on user settings) opens, and the second time, the window reloads, but the 3rd and subsequent clicks, a new window opens (with the same url).

The button code on the options.html page is:

<button type="button" id="customTagBtn">Custom Tags</button>

The code on the options.js is this:

document.getElementById('customTagBtn').onclick =
    function() {
        window.open("custom_tags.html","Custom_Tags","resizable, scrollbars");
}

According to what I have read, giving the window a name (except for “_blank” should prevent a duplicate window from opening, but it does not.

What am I missing?

On edit:

Yes, I know that I can use an if statement to fix this, I’m just wondering if this is a bug, which I should report, or a feature.