I know that ‘incused’ is not a good word, but it looks similar. For example.. I figure that since key fobs are often bigger to contain all the goodies inside, that it saves space to have a folding key–but why the change in the actual key design from, for example, something like this?
First guess: Cheaper to make. Multiplied by however many are produced = $$$ savigns for the auto manufacturers.
If your fob is separate from your key you have to somehow keep them together so you have them both with you if you need them. I have a 2010 Tundra with a separate fob and it’s a pain to have to lug it around in addition to the large key. My wife’s 2015 4Runner has the combination key and fob and that’s easier for me to carry, and lighter in my pocket, than my truck’s key plus separate fob. I don’t see any advantage to having them separate and I’m pleased that someone finally figured that out.
I had to go back and forth between the two pictures several times to figure out what you were talking about, but I believe you’re asking about the pattern on the metal part of the key itself, as opposed to anything to do with the fob or flipping. If so, the industry term is “laser cut keys.”
The VW companies - VW, Porsche and Audi - have been using “switchblade” keys for many years.