The internal device routing won't allow you to wire multiple level outputs to the same pin, as that would create electrical contention between multiple voltage drivers.
Can you explain what you mean by "2 parts sharing SCl and SDA lines"? The CYBLE-022001 only has one SCL/SDA pair on it iirc?
My board has 2 parts that share the same I2C bus. I got this to work by changing the SCB to be a multi-master I2C. Now I can talk to both parts.