It is but I'm going for weapon achievements while I play. Just finished Day 3 on MN and figured I'd tell you guys the strategy I worked out against the Gigantosaurus.
See, I got sick of waiting for him to fall over and decided to fight how I wanted to fight. I'll make a video if you guys want but I'm hoping this isn't so complicated that you can't work it out on your own. Basically, there's no need to wait for him to knock himself out. Just stare him down matador style and charge the level 1 UT on the Eclipse Scythe. Let it rip right when he's about to run you over with his head and he'll take some damage and the wave will cause a second hit to register on his tail, stunning him again and allowing you to get out from under him to other side of the arena. Rinse and repeat.
My recommendation, though, is to attack him normally until he gets his metal body. You deal much more damage when he's completely vulnerable by attacking him non-stop. This only becomes the better option when you can only attack his head. Also, don't forget to dodge to the side and hit Strong Attack when he tries to bite you before the last stage. You can get some free damage on him and a lot of people don't even know you can do that.
I've never heard of anyone fighting him this way before but if there is someone else, kudos to them I guess. I'm not much for claiming credit for anything. Just figured I'd help. Still working out my strategies to make it through MN difficulty at any player skill level. Up til now I've got something for pretty much every "difficult" fight.