April 13, 2022 Update
The braking issue is fixed and the truck returned to us last night. I've tested the truck numerous times and everything works fine. The work was done under warranty.
The issue was related to a programming/coding glitch with the newly installed electronic brake booster module. When this module is installed, the tech is to perform a "zero point calibration" of the ABS unit, steering angle sensor, yaw rate sensor, and accelerator sensor. Apparently this is a rare thing to do with later model 4Runners as they aren't often in for repairs.
When the module was installed, the tech performed the calibration which takes a while. The calibration shut-off thus the tech assumed the calibration took and the truck was returned to us. It turns out that the calibration did not take and simply timed out thus is the reason why the truck behaved so wonky under hard braking. It makes total sense as to why the brakes seemed to be working independently against each other and the truck rotating on its axis all the while the steering wheel straight.
According to the service advisor, when the tech test drove our truck, he nearly lost control during heavy braking. The service advisor even put in an email to me that the tech drove the truck and the braking is "
NOT" right at all. I'm glad I wrote a letter to the tech describing the issue in detail and to make sure that the tech understood to have adequate space to the right as that's where the truck will go quite violently if you're really hard on the brakes.
Once back in the shop, the tech ran a bunch of tests and he kept coming back to the zero point calibration. He tried the calibration multiple times and it would never indicate to him that it was done. It just timed out. To make sure this was correct, he called TAS and had an engineer walk him through the process. Turns out the current written procedure is missing a crucial step thus wasn't allowing the calibration to take. Once they figured it out, the calibration took. The procedure has been updated because of this.
It's rather scary how technology can work against you and what is designed to save lives could actually take them away if it's not timed correctly