Keep in mind the Platinum IIe did not come out until 1987 and the keyboard was specifically modified to match the IIGS keyboard, which does not have the same layout as the Mac Plus. Even when then Mac Plus went Platinum, no effort was made to update the keyboard layout, even after the SE & Mac II came out (which now that I think about it is a little surprising, considering that the Plus was sold for another 5 years, and the obscene amount of money Apple was making in those days). In fact nothing changed except the color. At least the Platinum 512Ke got the extended keyboard.
The 128K-Plus used standard "long-stalk" Alps key switches, but a common problem according to Larry Pina, was using short stalks which while compatible, required a different key cap, and later Apple ADB keyboards used key-switches from more than one manufacturer. My guess is that, at least the IIGS ADB keyboard and Platinum IIe may have used completely different key switches, despite the Platinum IIe's resemblance to the Mac Plus and its beige IIe predecessor.
So it's entirely possible that all of the beige Apple products used the same Alps key-switches at least up until the IIc and IIGS which were the first to change the keyboard design entirely. The Platinum IIe most likely just used the same keyboard circuit board that was being put into the IIGS ADB keyboard (which was likely derived from the //c), and therefore the same key-switches. Keep in mind the Apple II was made at a completely different factory (and state) than the Macintosh.