Staging Errors do not blow up lower Stage

[Apocrypha]

In .90 I've encountered a lot of little weird glitches that are not replicatable (like the "Launch" and "New" buttons not working in VAB) but this is one that is able to be replicated each time.

My only mod used is KSP Flight Engineer.

Given a simple rocket built Engine1-Fuel-Decoupler-Enginer2-Fuel-Decoupler-capsule. The rocket has a staging error, where upon pressing space bar, it does not activate "Decoupler" but instead activates Engine2. Thus, Engine2 begins its burn directly atop the still attached decoupler/fuel tank.

I would expect an explosion (and possible damage) to occur, however nothing untoward happens. Engine2 ignites as normal and propels the ship. I am able to decouple manually (by right click on the decoupler).

exact parts used are (from bottom up:)

LV-T45 Engine

FL-T800 Tank

TR-18A Decoupler

LV-909 Engine

FLT-100 Tank

FLT-200 Tank

TR-18A Decoupler

Command Pod Mark 1