Nice that they’re doing what they can to not leave people with e-waste bricks, but why would these be locked down in the first place?
It’s the wifi (not BT) connection that never worked off-platform.
From that starting point, allowing it to be a normals BT controller should require a minimum of additional work, but I think they probably had a reasonable business case to not do that:
We know they tried to implement to minimize additional latency, so I’m guessing they really did not want people using these as a general BT controller in case the user inadvertently connected to Stadia in that mode, which would have increased latency and reduced user experience.
Being able to plug in via usb for general controller usage was fine because increased latency there was not going to be an issues.
I suppose it all makes sense.