Unrooted does not mean secure
"In the three years since the Priv launched, BlackBerry has yet to see it rooted. BlackBerry wants IoT device manufacturers to adopt this as a quality mark. With so much insecure home tat flying in from China, consumers and industrial buyers need all the help they can get."
While I'd admit that all IoT things needs a hellava lot more security, being unable to root a device is not necessarily an indicator of security for your devices at home - and I wouldn't use this as a measure of how secure - ultimately - that device is (be it IoT, phones, et al).