Actually there are sliding doors between the cars. I have visited Toronto and rode in their subway.
There are no doors in that video. Related: According to press releases, Toronto Transit Commission (TTC) rolled out the "continuous" trains.
https://www.toronto.com/news/toronto-puts-new-subway-trains-into-service/article_d1cdc36f-f8e7-569a-a725-038210fac72f.html
(updated March 2023)
From the toronto.com article: "And perhaps the biggest change comes in the form of one long continuous train - a gangway - getting rid of the individual car style."
The design is a risk, not just for crushing people during a crash, or a security from an attacker, there's nothing to stop bullets from a shooter traveling the full length of a straight train.