I would argue that no, it's not an assumption of malicious intent, it's an assumption that Microsoft will not keep this data private and contained. It will leak

I would argue that no, it's not an assumption of malicious intent, it's an assumption that Microsoft will not keep this data private and contained. It will leak, either to governments (which Microsoft has time and time again helped without a question of whether they should) or to other non-scrupulous actors.