I wanted to give a final conclusion to my experience with the break squeal in reverse.
Lexus did their TSB on my LC FE and since preforming the service, my brakes have been silent.
I spoke with the shop foreman as he took a test drive with me, before and after, he said that he inspected the old and new pads/rotors/shims/etc. and he could not see any differences visually.
He said that in his experience when Toyota/LEXUS (in this case just LEXUS) throws multiple parts at the problem, the engineers either are unsure which individual part is causing the issue or the way the entire system is working together causes the issues, so they replace the entire system.
I asked why Toyota had not released the TSB while LEXUS had and he said that LEXUS will release TSB for annoying issues (because luxury brand) that are not directly related to safety while the Toyota side generally does not. He felt that was very unfair especially for vehicles like the LC which are expensive regardless of the badge, but that is why in his experience
Either way at least for now, the LEXUS TSB has solved the issues as I wrote earlier, my brakes have been silent.