What does verification procedures show is that the code used for the wallet is public, it can be built from source, and the binaries match the published source code on GitHub. Like you said, Keystone 3 passed those tests six times.

But Wallet Scrutiny does not audit the code for bugs and vulnerabilities. A wallet that passes all audits can still be malicious. I am not saying it is, just that it can in theory. I am sure there are security experts who have vetted Keystone and its products, and you will need to trust that they did a good job. It probably hasn't been put under the miscroscope as close as Trezor, for example. That isn't necessarily a negative thing.