Probably every company has said that, yet we know how that usually turns out sooner rather than later (I'm looking at you, WhatsApp).
"So I know it's not easy to believe, and it's easy for me to say since I work here, but nothing nefarious is going on. If there was, we the engineers would be against it completely."
For now. What if a new higher manager comes and decides to use this information for other purposes (ad, sale etc.)? Some engineers might quit, but costumers can't take their data back.
My takeaway is: do not trust companies with more data than necessary to provide you a service and this is exactly such case.