Can someone help clear up something for me?

First, all packs purchased during the presale (including bonus packs received) will be eligible for a chance to receive ALL 13 new cards that will be airdropped every time the next 1M Chaos Legion packs are sold over the life of the set.

Why is this paragraph in the "Presale Rewards" section? How is this any different than buying packs during the first week of the general sale? Because those packs would also be eligible to receive all 13 airdrops, no?