>> it's not as if rapidly opening and closing a tab actually takes effort. It may be faster than the long click depending how comfortable you are with keyboard controls.
For normal people, i.e. those who aren't techies, you have your answer right there on why this may be useful. We are very efficient with our browser usage. Normal people struggle with this task because they get lost in the steps. Even if they can do the steps at a slow pace, it doesn't stick because it's too slow. The leap to using keyboard shortcuts just won't happen for the majority of people.
I think your points on how this is implemented are fairer. That said, that said it seems like the best approach is to follow the simplest and most efficient approach, which is to not load extensions, or use what is loaded.
The success of features like this is known with technical users like us. We don't like them because we have a workflow that avoids the issue like the phishing one you describe. It's unclear whether this helps users and is likely somewhat experimental. I think it's a much better place to be doing work that other areas where they have invested even if it has many issues.