From the POV of the DDM, antimatter would be easy to detect and declare either categorically inedible or at least categorically threatening. Things like fusion powerplants, or stores of chemicals with the potential to release destructive energies if combined, would be much more ambiguous, and probably edible as such - unless a malevolent power turned them into weapons at the last second.
Was the DDM a weapon? It did not seem to pursue tactical goals, such as eliminating threats. It just demolished and ate, and growled at those who attempted to intervene. If the DDM was merely a reverse terraforming tool of sorts, it would not systematically and strategically act against potential threats, and would have no particular reason to scan for devious hidden bombs.
The TOS practices on photon torpedo use warrant some examination, too. In "Arena", torpedoes were used against a target at extreme range, while the landing party fought at long ranges using a possibly similar weapon that apparently posed a great risk to the user in closer combat. In "The Changeling", a single torpedo was a seeking precision weapon used against a nearby but extremely small target. In "Elaan of Troyius", a spread of torpedoes was effective at medium range in a warp fight (or possibly a warp-impulse-warp strafing fight), while in "Journey to Babel", it was ineffective at close range.
This spectrum of uses or attempted uses would seem to rule out most of the tactical limitations we might imagine applying to the "DDM" situation. The maw of the DDM would not be too close ("Journey to Babel"), too small and difficult to hit ("The Changeling"), or too distant ("Arena").
Then again, if torpedoes are the preferred weapon in long range or high speed fights, "Arena" and TNG era style, it would make sense for Decker to have tried them out in his reputed initial long range engagement. If they proved useless there, Decker would not try and use them when commanding the Enterprise