Google Support says Pixel audio issues are related to the hardware

[mbrowne5061]

If all of the phones had shipped with proper software, keeping the volume below distortion levels, would we have said there's a problem? Certainly not

Now if speakers were to completely fail after some time we would call it a hardware problem.

True, but reviewers probably would have complained about 'weak' speakers with 'small' sound. Just because you limited with software doesn't mean its not bad hardware. A properly built speaker shouldn't need artificially-imposed software limits; you design it with the proper number of turns in the electromagnet, the permanent magnet has the correct Tesla and Henry values for the electromagnet and desired operation, the diaphragm is the right shape and size, it's all supported by a rigid mechanical structure that vibrates as predicted, and you use the right materials for the job. Google failed at this, and is now 'correcting' it by limiting the speaker by taping he volume knob lower than designed.