Google struggles with presenting a unified interface, design language, and overall experience across their scattered hardware platforms

Agreed, but that to me seems more of a conceptual and software issue, rather than the hardware side. Although the article makes it seem like the teams getting merged are also (at least partially) responsible for that:

Currently, all three teams operate separately, making standalone decisions on things like design, software, hardware engineering, etc.

However they also need to be more reliable to build an ecosystem that people buy into. It’s kind of a meme that in every google thread killedbygoogle.com gets mentioned, but there is truth behind it. Especially in the smart home space you really need to project long term support for people to buy into your product suite.