The problem is Greenworks not eBay or the seller. Sounds to me like Greenworks has changed their polices. Nearly 4k Greenworks tools on sale on eBay right now
I saw nothing on their warranty page that looked unusual, seems more like you have to buy from a normal retail channel, not some random 3rd party reselling gray market goods, which is how warranties are handled for most companies.
I agree that shipping something back is a hassle, but I'd much rather have a refund. Why would I want a widget that is prone to failure, repaired then I'd expect it to keep failing again in the same way? I want the money to buy something else instead.
They need to publish a list of who are authorized sellers. And improve their means of customer service contact.
I agree on both issues, but when I buy something I have a pretty good idea if it's an authorized seller versus some random joe with no warranty.