Hi Carmen, yes I saw this message too and felt slightly uneasy about sharing this information with no clear explanation, however, after looking at the notes it does say you may be removed from airbnb and not receive any bookings if you fail to share the information.
In the UK, we have the Rent a Room scheme (you may already know this) which currently allows you to earn up to £7,500 tax free if you let a furnished room in your house (it only applies to rooms, which are part of your home). I am currently operating under this as I do not intend to earn more than that from my letting in this current tax year. If you go over this threshold you must declare it and do a self-assessment (tax return). I understand that Airbnb is allowing many people to earn additional income to their normal everyday jobs and I suspect that governments worldwide now want to be sure that all due taxes are being paid and one way for them to do this is collect data through Airbnb rather than relying on individuals to regulate themselves. I am going to speak directly to the support team and then will share the required information with them. I'm sorry if this doesn't answer your question but sharing thoughts can sometimes be helpful. All the best.