I have a 5th gen, so this doesn't answer the OP's question directly. But for what it's worth, since this thread is in general discussions.

I was able to pick up a rear wiper blade assembly (rubber, replaceable part of the arm) from my local Carquest. I forget the brand, this was several years ago. I do remember it was claimed to be an exact fit.

I got home to find that the package came with several adapters, so obviously wasn't exact fit. The directions on the back were vague and none of the adapters looked to fit my wiper arm. My '18's owners manual doesn't outline how to replace the rear wiper. Just a generic "take it to your Toyota dealer" verbiage. My problem is that my Toyota dealer is 135 miles one way, 175 miles away the other and 245 miles away in yet another, and nine hours away in the last direction of the compass.

I tried the adapter and diagram closest to what my arm looked like and followed it's unwritten but illustrated direction on how to disconnect the arm. It was soon obvious following that would break the arm. After spending nearly two hours looking through the encyclopedia size owners manual and attempting to install my wiper, I gave up.

Frustrated, I spent some time searching online if I had the correct wiper and how to replace it. I had the correct wiper. I probably spent another hour watching amateurish videos - you know, those that the You Tube sensation is trying to hold his phone in one hand and trying to manipulate things that require three while dropping their phones, the video quality causing epileptic seizures because it's moving at light speed all over the map, cussing, endless mindless drivel instead of verbal instruction? But I finally stumbled upon a simple, well done video by a Toyota dealership service department on how to replace my wiper blade on my 4Runner. It was only 30 seconds long.

I timed my attempt after watching the video several times. It took me 74 seconds to swap out my wiper blade. I wish I bookmarked that video for future reference.

The wiper is several years old now, but still in good shape because it sits up within the housing hanging over the rear window. But the rear window gets very grimy in wet or winter weather, so the blade takes a beating from grit and grime.