The YTDL version doesn't necessarily have the Google adverts in it.
That's a loss of "revenue".
As for the method, the download tools can do:
Byte range
0-100000 \
100000-200000 \
200000-300000 \
300000-400000 \___ The downloader can open seven connections, and even if
400000-500000 / a connection is limited, this way they get 7x the limit.
500000-600000 /
600000-700000 / Servers can limit the number of connections as well
as the bandwidth per connection.
If John and Mary are in the same house, and using Youtube at the
same time, the IP address of the requests is the same for both of them.
The server then, has a problem in that, if it is "careless", either John
or Mary might not get the service they expected.
If each client is carefully labeled enough, then the server might be
able to police John and Mary to one connection each (such as might
be used by the video player). But even their video player might
use byte ranges, so the mode likely still exists.
There are a few degrees of freedom to the problem, of policing
without screwing up the service. But if done right, then all
those users out there get to enjoy endless Grammerly adverts :-)
Worst case, a YTDL should still be able to capture at 1X.
So a 60 minute movie, takes 60 minutes to capture.
That's the ideal state from Googles perspective, even
if the adverts aren't mixed in.
They can't practically mux the adverts into the vid,
because that takes work. It's easier (especially on my news sites
here), to play the advert as a separate video, so you can rotate them
willy-nilly and a client sees the same advert less often. That's if
they have enough adverts to serve. Most users are sad pandas, if
the same stinking Grammerly advert plays over and over again.
Paul