I suspect that you are correct. The two downsides to using sapphire are its high density and (presumed) additional cost. If Apple have perfected a thin laminate at reasonable cost then that will be a significant breakthrough.
I'd accept that might be a reasonable explanation if you had experienced it on just one phone, but two phones and their replacements? Maybe you have been inconceivably unlucky but, that possibility aside, your story does lack credibility both in terms of the problems you describe and your actions, so you should not be surprised at the incredulity in some of the responses. And I'd advise against the use of the F word - it doesn't sit well around here.
The two biggest risks to the screen are scratches and breakage, and sapphire definitely provides scratch resistance that no glass variant will approach. As for breakage, sapphire is stronger (higher compressive, tensile and shear moduli and higher yield strength), but has lower strain to failure than GG, so it won't tolerate bending as well. However, since the iPhone is a fairly rigid structure, that should not be a huge problem.
I'm curious. If, as you say, you live in another country where these agreements don't matter, and have no loyalty to Amazon or Apple, why are you devoting so much time and effort to researching this issue and arguing on this forum?
By toughness, you presumably mean fracture toughness? If so then it is lower than for many metals precisely because it is hard and has a low strain to failure. But remember that fracture toughness is fundamentally a measure of the stress required to propagate an existing crack, and that the advantage of sapphire is that crack initiation is difficult because of its high tensile strength.
Right - data leakage has been observed many times, but not cellular data leakage with the radio turned off. The complaints are generally that the phone switches to cellular even though it (supposedly) has a wifi connection. But you said that you turned cellular off. Did you not mean that?
It can be a little hostile, but it is also important to pay attention to whether you really are just expressing an opinion, rather than asserting that you are presenting fact. It appeared to me that you strayed the wrong side of that line.