Had a similar experience, only I got the achievement without the cursed Greatsword of Artorias and ascending the Greatlord Greatsword as the second last weapon. It's the second time for me encountering this on different PSN accounts so my guess is that the weapon ascended can be interchangeable as long as theres two boss weapons from SIf?

The gravel or sword is on this list lol, how is everyone missing it?

This is true, you need the Gravelord Sword for the trophy/achievement

I believe that you must have them all on the same character. This would mean that you have to go at least till NG+1, if not further depending on whether or not you're going for other achievement too.

Yes same character is required. It has been said some people got it on different ones, but that is most likely a glitch.

It doesn’t track who made the weapon, just that you have them all at the same time.

you could just farm the materials before crossing to the new game and upgrade them on that cycle