I've deleted a lot of accounts in the last few weeks, and Airbnb was the only one requiring an ID prove. I agree, it is indeed part of GDPR for them to ensure I have the right to delete my account. My only issue is that my ID does not prove anything in my case, because Airbnb doesn't know my identity which they could compare my ID with, because I did have to provide my ID after registering and I never booked anything on their site.
