Great question! One of my colleagues verified with his KICKR Bike.
KICKR Bike and Play can be paired as steering devices simultaneously if both are paired over Bluetooth LE (BLE). The bike’s U-Turn and gradient buttons work while Play is paired.
*If KICKR Bike is paired over ANT+ and Play is paired over BLE, an error notification appears on the Pairing menu stating the devices aren’t compatible with each other. This is relevant to Windows and macOS users who have ANT+ capability with a USB dongle. iOS and AppleTV do not support pairing over ANT+.
It’s also important to note the braking behavior of each is different. Play braking will only slow your avatar down. KICKR Bike braking adds resistance to your trainer (ultimately slowing your avatar).
*Note- pairing behavior over ANT+ is as of June 2023. This may / may not evolve over time.