If the specs are bad, QA will find low quality spots of undefined behaviour (anything goes, ergo it's fine), or even actual logic issues in the specs.

However the software is coded to specs, not to QA's own desires, so the bugs stay.

It's a rubber stamp like many other things in this development model.

Not saying their QA is useful, but it's not tough to imagine their QA being many layers removed from decision making. ie: Program Manager -> Product Owner -> Project Manager -> Business Analyst -> QA -- not even mentioning reporting lines.

That person in QA at the end of the chain is likely following a script written & approved by the layers above them to a T. It's highly unlikely that they are empowered to go off script or raise tangential issues. Doing so may even cost them their job.