I'm a US firefighter, our department doesn't vent until the engine has water on the fire. And even then we pay careful attention to where we vent. Can't speak for other departments.
I would agree that most of your examples show poor tactics and/or poor training.
However the first video appears to show proper vertical ventilation. There is a charged hose line into the front door, they are either putting water on the fire already or will imminently.
I'll cite a UL study on the topic. This paragraph is from the summary, and it highlights the importance of coordinating ventilation with the attack team, but does show that it can greatly improve conditions for the interior team(s)
Here's a link to the full study, it's a long read but very interesting.
With that being said, my dept usually doesn't ventilate residential roofs because the reward generally doesn't outweigh the risk. And horizontal ventilation is almost as effective.