But this is a pretty extremist take. Just because a company doesn't push source code and you can't deterministically have 100% certainty, doesn't mean you can't make any assertions about the software.
To refuse to make any claims about software without source is as principled as it is lazy.
Imagine an engineer brought to a worksite, and they don't have blueprints, can he do no work at all? Ok, good for you, but there's engineers that can.
Reversing the software is table stakes for assurance work already so suggesting source is a requirement just doesn’t match reality.