(Question) What happened to the 'progress' event?

[macfitzwool]

Hi there. I have been digging around to find where the event that is documented on both the repository's readme and relevant examples folders.
These examples simply do not work as these events never fire a response, neither does my IDE (vscode) does not autocomplete for 'progress' event anymore.
Any previous issues in this repo seem to point to older versions of the library or are quite old now. None seemed relevant to what I was trying to figure out.
Code where I was trying to use this event:

let audio = ytdl(url, { quality: 'highestaudio' });
audio.on('progress', (c, d, t) => { // <= this *never* fires or is recognised!
    let progress = (d / t * 100).toFixed(2);
    // ... (rest of progress monitoring code)
});

Has this event type been deprecated in a previous version or prior to v4 of this library?
I have not seen any mention of it in previous versions other than back in v3.3.0 so am mostly guessing support for this feature may have been removed or it somehow is not working anymore.

Version Information:
Windows 10 (64 bit)