spoiler information below. do not look if you are interested in finding the urns on your own.
okay my bad there is a mistake above about the difficulty being grayed out and this is why below.
okay, the part where start a new game. i was wrong about the greyed out part it will be selectable if you have completed the game. the reason i stated this is that when i did my original testing, i used my primary profile. i have 2 user profiles on my PS3. when i began to play god of war for the fist time ever, i use my secondary user profile to play the game and completed the game and did not get the boss batch 3 trophy to unlock. so to test my theory on not getting any urns i used my primary user profile and started fresh where you could not select the TITAN difficulty. that is why i stated this, sorry for the confusion this caused. it was just part of my testing so i could verify my theory about the urns being the problem. so after i completed the game without getting the urns, the boss batch 3 trophy did unlock after killing the 3rd sister of fate. now i tested that idea in my secondary user profile. i started a new game by selecting the very easy difficulty and selected no to playing the bonus play. that is how you begin a new fresh game so that you do not begin with the urns and other unlocked items. you need to select no and begin a new game without these features unlocked. i did not obtain any urns during this game and in doing so made the game go by faster. see below for clarification about the backtracking.
yes by backtracking i mean: urn 1 you do not move the block to its location and bring the block back to continue. just ignore it. urn 2 do not backtrack to get it. the only way to get it is obtaining the fleece to deflect the stoning beams at that area past the water wheel. do not backtrack for it. urn 3 do not run back by using the time stopping amulet. do not backtrack for it. urn 4 you can just pass by it do not get it. if you are in easy difficulty there is no need to get any extra chests that are with the chest that contain the urns. but if you do want them i would say that will not cause any issues because i think i did grab the eye and/or feather at those locations. again my bad on the difficulty thing. sorry.