A quick update on this, we discovered a minor difference in how the LIFX buld acts depending on model, which created this issue.
We have now fixed this so we will soon release a new firmware update which makes this work!
I'm sorry to say that Siri is still not possible because of a change that was made to CoreBluetooth in iOS. We still don't know if this was intentional or if it is a bug. Apple has not explicitly said that this is not allowed, but after having submitted bug reports to Apple and getting no response at all we are not very hopeful at this time.
I'm sorry about this.