[Login to see the link] - I'm not entirely certain what you're arguing. I explained your backend explanation is correct; however, you appear to be hung-up on the terminology of "token". I'll try to be more clear --
A "token" is a contextual term referring to how a key is used. It's complimentary, not exclusive of the term.
I'll put it more simply... When you pass information to be used for purposes of passing a test (to oversimplify -- eg - login or DRM), you could refer to the specific type of information, such as a "key" (in the case of encryption) or "credentials" (in the case of a login), etc.
However, the context of --supplying-- the key is known as "passing a token".
The fact that you refer to a login as a "token" does not in any way, mean that a "key" cannot be used as a "token".
Think of it like the private key in public/private encryption, where the public key is known as a "token" because it's passed to be used/tested with the private key.
I hope that clarifies and misunderstanding about the English use of the word "token" vs "key".
Back to the original point... Whether it's a cookie or widevine DRM key, everything needed can be obtained in the HTTP headers.
Speaking of HTTP headers, that reminds me that Udemy, unlike Lynda/LinkedIn, etc -- sometimes (not all) has been using widevine DRM recently, which requires the bearer token/keys (this can be pulled through Firefox dev tools; it's more reliable than Chrome for this purpose) and/or worse case, decrypt with something like N_m3u8DL-CLI.
...Back to my original point, and my original offer to help sanet users...
This question is very common on sanet, therefore... If someone would like me to write a tutorial to create a "sticky" for Udemy ripping, I will be happy to do so.
My suggestion would be to write the tutorial as it applies to most sites. Those sites that are starting to use widevine DRM, I can add the extra steps to obtain the added details, if that helps.
And/or, if anyone needs proof of how this method works, I will be happy to rip a Udemy video, if there is one that many people need, which hasn't already been uploaded.