This arguments are the ones used and shared by Olympic coaches. There is nothing new in what I say. It´s well known in sport circles that science goes between 10 and 20 years behind the Olympic training methods. They don´t have time to wait for studies to happen, they need to go for what it works now.

As I said HIIT is very very useful, possibly more effective than beginning as I said (depending of your objectives): developing slowly your capability over some months. But recommending it to people out of the blue, with out proper training time under their belt (doesn't have a minimum adaptation to physical activity) that don´t know how their own body reacts. It's just an injury waiting to happen. Not only that, Hiit training is so exhausting that a lot of people give up before they can see results. So one thing is to say that it´s effective, and other to say that it´s really useful or safe as it´s recommended, after all we are talking of finding a training system that it´s useful to the average guy who wants to start training.

IMHO it's much better to make a plan that makes you start slowly, with low volume and low intensity. And from there over the months (you don´t need a lot of them, 2-3 months is more than enough to develop a training base), start adding HIIT, etc.. But that's more difficult to sell, as we all want results this week.

What stretching does, is to allow a complete range of movement, for example people that perform bench press as their main exercise usually develop a strong forward tightness at their shoulder girdle (besides not stretching they usually don't balance the strength between pulling and pushing).

They are terribly strong in one movement (pushing), but this tightness and lack of balance helps develop a lot of shoulder problems overtime, and even it can stop the body from further developing the bench press strength. It´s more complex than only stretching. But stretching has it´s place, you only need to look at Gymnasts and Weight lifters, that are the most powerful athletes gram per gram (of relative strength, not absolute like power lifting). Both of them are very very flexible compared to the average sport practitioner. They develop that stretching capability because they need it to perform well. At that level you don't train a property that you don't need. Of course circus levels of flexibility are way too much and could lead to problems.