There is nothing in the 3.0 rules to support this view. A large dagger is not the same as a large greatsword. If -you- treat it so, then that is a house rule of your campaign.
First off, the ability to have every weapon available for any character regarless of that character's size is a significantly useful thing. In 3.5, I can make a single weapon entry for a new weapon (such as a Falx) and there are clearly defined rules for use of this weapon by anybody regardless of size. This just wasn't true in 3.0. Look at the AU weapon lists; you've got entry after entry of weapons that vary only by their size like Faen Shortaxe, Sprytebow, Giant's bow, Faen nunchaku etc. None of this is needed anymore.
Overall, I find the newer rules much less complicated than the old ones.
Aaron