I do this same thing on darker roasts. It works well with immersion brews like the French press, aeropress and Clever (presumably the Hario Switch as well, but I’ve never used one). It’s a YMMV thing, but basically it’s a good technique for beans roasted dark enough that you don’t actually want to extract every last bit of flavor compounds out. Once you extract past the initial roast there are the pleasant nutty, caramelized sugar and dark chocolate notes that are so desirable in dark roasts. The goal is to get those without pulling out the burnt wood and astringent charcoal flavors just beyond. It can make for an amazingly smooth cup. Just be sure to use enough coffee so that it isn’t weak.
With lighter roasts I will go all the way up to boiling if needed. Under extracted light roasts are not my thing at all. At a certain point with some of those you lose so much heat when the water contacts the coffee bed and brewer it can be hard to extract enough.
I totally agree with you. Based on what I have learned about advanced coffee making, ( Remember folks, my journey never ends, it only gets better as time goes by ) you want to use a lower temperature 195F when you are brewing a dark roast, this way you don't extract a bitter flavor out of the beans. Where as, with a lighter roast, you want to go with a higher temperature 200F+, it helps to maintain that overall sweetness one would expect with a lighter roast.
I have Stirling Kenya Sweet & Bold Dark Roast Espresso & Stirling Ethiopian Yirgacheffe Sweet & Bright for my Light Roast. Each of these have to be brewed differently to achieve a perfected brew. And additionally, I find, when using a lighter roast, more grounds are required, to achieve the same space in mass, in the filter basket, and to secure a nice smooth juicy berry flavor, with my Ethiopian Yirgacheffe coffee.
Where as, with my Kenya Dark Roast Espresso, I need to use less grounds to fill the basket, and also to control the strength of the brew that comes out. This is another reason why I want to get a proper brewer, that doesn't limit me on space in the grounds filter basket. I want the freedom available to me, so that I may lock in my coffee to water ratio's, to secure perfection. Yes, I am like the Borg, I will not be satisfied with anything less then perfect. LOL!