I don't understand how walking in the study is considerate moderate.

Like my heartrate for sure goes higher when lifting weights than when I walk. If I walk fast, it might get closer, but I am not that confident.

300 minutes of HIIT per week are equal to 10 HIIT sessions per week, I would argue that's outright impossible, the body cannot handle that, I don't think even an Olympic athlete can handle more than 3 times per week HIIT.

Vigorous might be possible, that's still 5 times 1 hour cardio sessions, on top of which you have to add 3 sessions of weight lifting for bone density, on top of which you have to add balance training and stretching.

There isn't enough time in a day to do that if you work, let alone if you have kids