The information comes to us not from Lenovo, but from the manufacturer of these analog keys: Peratech. In a press release cited in source below, the company walks us through the feature in detail.
Like a left stick on a handcuffs, ZQSD keys are traditionally used in-game to perform moves. However, there is usually only one speed, and pressing another key to start walking or sprinting is necessary.
This is where the term “analog” comes in, since it makes these ZQSD keys sensitive to finger pressure. The harder you press the key, the faster the movement will be.
Such a thing was previously difficult to integrate on a PC portable, due to the size of the keys on the keyboard. Good big mechanical keyboards often feature thicker keys, around 4 mm. To offer a good compromise, the keys of the Legion 7 and 7i are 1.5 mm thick, in order to allow a certain pressure distance and thus make possible the integration of analog.