The original lean was actually 40 degrees on the camera, and the players spine would only bend 20 degrees. So you would run into issues where you could lean around a corner and an AI would be looking right at you, but technically you'd be totally hidden. It made 'em look really stupid and also gave you a massive advantage.
So, if you increase the spine, you run into really strange issues where the player bends unnaturally. Thankfully, there's a solve: use your free-lean. It's been slowed down and polished so it can be more useful + less janky when you need to lean wider! :)
You'll still be slightly safer leaning and clearing around a corner, and we still have some improvements to make (the lean being diminished while moving will be removed).