I'm very skeptical of WhatsApp's security but I'm also very skeptical of these ad claims. We've seen a tone of those over the years, these companies would have

I'm very skeptical of WhatsApp's security but I'm also very skeptical of these ad claims. We've seen a tone of those over the years, these companies would have a lot to lose if they did that. Chances are that you're either more predictable than you expected, or it's just random chance and correlation bias. Billions of people use these services, there have to be some freaky coincidences happening all the time. We need something a lot more solid than "I've heard people" to make any conclusion. But the general point still holds, it's a closed source app made by a company that thrives on data mining, of course it should be considered insecure by default.