That timelapse does not show even remotely near a million people. To put a million people into perspective, the entire population of Paris in 2019 was 2.161 million.
The AP article I read on this subject suggested there were around 100K protesters over the entirety of France :
https://apnews.com/article/europe-business-health-government-and-politics-france-d25494f4cf4ca6c6d1464188a89ece6f
Over 100,000 people protested across France on Saturday against the government’s latest measures to push people to get vaccinated and curb rising infections by the delta variant of the coronavirus.
Another article written about past protests in France (it was an old article about protest strikes in France) pointed out how difficult it is to accurately count a protest:
https://www.thelocal.fr/20210127/why-can-france-never-agree-how-many-people-are-protesting-or-on-strike/
It is true that I have no experience at all with putting accurate numbers to crowds. As a filmmaker I do have keen eye however and what I noticed were the numerous side roads which were also packed full of people yet the cameraman chose not to go down them. My point is that we didn't even see the full scale of this protest. The only way of course would be looking down from the air. With a lovely high resolution photo ideally. If only I had been there with my drone this is what I would have provided for you! Alas, we make do with what we have and make estimates the best we can. That being said, 100,000 across the whole of france is a joke to me. Not a chance.