I'm not sure it does make any practical difference, but I could be wrong. But as someone who has been a little bit involved in the process since 2010 it's an enjoyable personal milestone. And I'm really happy for all of the wonderful people I've met along the way who contributed way more than I did.
The W3C usually adds new specs years after major browser vendors implement them. A browser being created after that time would be expected to be compliant with W3C specs.