While Switch is 360-esque now, the Wii Classic Controller had symmetrical sticks at the bottom, Wii U Pro Controller and GamePad had symmetrical sticks on top. So Nintendo wasn't totally committed to the 360 design even if the GameCube controller was almost there before. (Not gonna count the Wiimote as it's a little too different) Steam Deck and Steam Controller have symmetrical sticks as well. I don't think it's as clear cut as you say. 8BitDo and GuliKit have controllers in both form factors also (released in the last 2 years even).
Also worth noting that XInput has been holding back PC controllers so that anything more ambitious than a 360 controller is hard to get working. Microsoft is also the only controller manufacturer to not put gyro in their controllers.