I think I understand why eBay has that rule. Maybe confusing, but sensible and with good intent.

Let's say someone, who has only $1000 to spend on paintings, bids $1000 on a painting in Auction #1, but he didn't meet the reserve, so he gives up on that painting and takes a look at auction #2 where he bids his $1000, and either wins it or is high bidder. It would be embarrassing, to say the least, if the seller in auction #1 then lowers his reserve and, automatically, our bidder ends up winning auction #1!

To prevent something like that must be the reason for the eBay rule.

Robert