Ignoring that Poop shouldn't be dealing more damage given the skill description (both languages), that item also has the issue of despawning over time on higher difficulties. Also, at least at "entry level" SUR, the damage difference between Poop and a Rock is pretty negligible; not really worth going out of your way to eat 4 food items each to generate the items en masse on location.
Maybe it's just my play style, but again, this is more a matter of regularity. One of the most ideal situations to use traps is where you don't want to get spotted - and those maps tend to have at least a half dozen mobs to deal with. Since a single FMH eats up a full quarter of starting carrying capacity, using them to incapacitate 8-10 mobs simply isn't possible (nor all that cost-effective). Further, since said mobs on these sneak missions also tend to be in the 60-150 hp range early-mid game it's hardly worth it, either. Even the most cost effective weights (I believe this is spear/pitchfork/pickaxe) are prohibitive in the sense that Frag Mines can easily do 2-3x more damage at half the weight profile.
Despite doing mediocre damage, Rocks have the benefit of having no weight profile (all you really need is at least 3 "free" weight), so you can place as many traps as you want without really having to concern yourself with weight issues.
As such, I would still argue that given how more often than not using a Rock is the most ideal "standard trap" form, the game should probably not roll through EXT-1 to EXT-5 to create a trap by default, and rather do that on a Shift+ action.