It’s KYC and nothing else. Loads of financial institutions need to do it. Amazon need to do it. And generally, passport and driving licence is what is suggested because MOST users will have this. So it makes eBay’s life easier if you can provide this. There is a way to provide a birth certificate and you can, you just need to jump through more hoops as you are an outlier. Most people will have what eBay would prefer.

to think eBay are for some reason doing this to data harvest your passport photos for some nefarious purpose is a wild, wild reach.