Rear Brakes squeaking with truck stopped

So today I went to pick up something on the bed and noticed that when a bouncing motion was made, the rear brakes would squeak. If I press the brakes and have someone do the bouncing test it doesn’t squeak. Is this a Tacoma thing? Truck only has 19k miles. I’m attaching the video of the sound it makes.

 

Video
https://youtube.com/shorts/3QDoT8dfxn8?si=VrPPNPTnGY0D8GUz

 

Also this is very intermittent and doesn’t happen all the time. I went for a drive now and decided to do the “test” and it’s quite now.

 

Not the brakes.

It's the leaf springs.

Common and multiple 'fixes' can be found here.

 

Would it stop when brakes are applied? I had someone do it while I was under the truck and it seemed to come from both rear brakes and not the leafs. I thought it were the leafs at first as well but the noise immediately stopped if someone pressed the brakes and bounced in the bed.