So the only time difference is how long you take to ship them the broken card. IME, they shipped the replacement the next day after receiving the broken card. So the difference between an Advanced RMA and a standard RMA can be as little as a day or two.
Now, as for why eVGA is doing it this way. Well, lets just assume you are a scalper that has no moral integrity. You get an eVGA graphics card that you plan to scalp. Now though, eVGA is giving RMAs to anyone that says New World bricked their cards. So you just apply for an advanced RAM, pay the $700 MSRP, and turn around and scalp the second card too. Now eVGA is out the second card, you aren't actually breaking any laws and eVGA can't go after you because you paid them for the second card. That's the whole deal, you are paying for the card that they are shipping you in advance, if you don't return the "broken" card, they keep your money. But a scalper now just got two cards at MSRP that they can now scalp. However, if eVGA charges scalper prices for the advanced RMA, then it isn't worth it for scalpers to run the scam to get more cards.