2. If you're a NSA boss, and some of your experts told you that you can break SSL in Apple products with adding one line that could be almost certainly attributed to inconspicuous human error, would you try to make a deal with Apple?
3. If you're an Apple boss, and NSA offers you cache (or other benefits, like competitor intelligence) for adding plausibly deniable bug in your code, would you turn it down?
There is no direct evidence for this case, sure. There is however ample evidence in the Snowden docs that this scenario happens too often for this to be called bullshit conspiracy theory.