The fix actually changes the way algorithm deals with blocks that are timestamped before the latest block's timestamp (ie timewarped blocks). It processes them just like if they were timestamped as the latest block. So if there is any benefit an attacker gets by timestamping the blocks in the past, the benefit will be gone. The attacker could as well timestamp them with latest blocks time. No more any extra gain from Time Warp, whatever it has been.

This change actually lowers the difficulty what the time warped block would get. However, the attacker would get the same lower diff by timestamping that block at the latest block time, ie not using timewarp, so the fix does not give any advantage which had not already been there.