A controlled Warp Core Breach was "Auto-Destruct System: Plan A" where the reactor basically fires alot of Matter & Anti-Matter at each other without the Dilithium to controll it. This was intentionally done to create a large enough explosion to vaporize the entire ship at once.
That's "Auto-Destruct System: Plan B" incase the first system failed for whatever reason and you really need to destroy your own vessel.
Indeed. Scuttling charges can be designed to be quite safe and only will go off at the appropriate time.
That's because StarFleet doesn't isolate the local power systems in their rooms from the EPS Conduits and the local EPS Taps. That translates to running most individual rooms off a direct connection to the EPS Tap in each room..Considering how easily normal systems such as consoles explode at the slightest shock, it would seem unnecessary to have additional explosive materials stashed around the ship.
Kor
Unless those torpedoes are stored right next to the important bits, such as the computer core, and classified access points, additional explosives at critical systems they do not wish to fall in to enemy hands would be prudent.
The idea that it was done on purpose for those reasons in TSFS requires a hand wave. It was the same code sequence entered as was entered in "Let That Be Your Last Battlefield," when the ship was alone and warping through interstellar space and destruct was ordered to prevent the ship from falling into enemy hands. Kirk gave no order to the computer for minimal destruct to avoid collateral damage.
