I do not think this is a money grab. As has been highlighted by all the "Ebay outed auctions" of clear fakes here on Net 54 - fakes have proliferated for years with likely unsuspecting buyers getting burned. An authentication process for higher value cards makes a lot of sense in instilling confidence for buyers that they are not getting burned with a fake card and are covered if they do.
Questions, as have been raised in this thread, will have to be answered in practice over time - 1) timing - I imagine would be exponentially faster to deem authenticity rather than grade - caveat - does the authenticity guarantee no alterations and what is considered an alteration?
2) cost - time will tell 3) Is CSG the right choice or the new kid on the block willing to work for Ebay's offer to try to gain some market recognition.
For now, I like the concept.
Edited to add:
In reading through the FAQ's - I see 1 potential red herring - part of the "authentication" - they are going to match the card to the condition description:
https://pages.ebay.com/cardconditions/
and if those condition definitions are from CSG, then I have a clearer picture of why I will not touch their cards with a 10 foot pole!