With a lot of the adult-oriented sets (ICONS and others), especially anything plant-based, they go out of their way to point out how they're using existing pieces in an unusual way. One example is the cherry blossoms on the bonsai tree are actually frogs, but cast in a pink color for the first time, called out in the instruction manual as you're building it.
I love it, knowing about these little details. Also fun to share with friends that inquire about the various LEGO on display in the house. This, and all the fancy mechanics (e.g. typewriter, nintendo), engender a ton of respect and awe for the designers.
I've talked with a Lego designer before, and for some themes they're not allowed to even request new molds. Even new colors of existing pieces can be contentious. My own head canon about the bonsai set is that the reason they made such a big fuss about having the recolored frogs is because it probably was a big fuss internally too. "Who'd ever need pink frogs?" sort of thing.