The majority of those conditions (dates, block heights, difficulty levels, transaction amounts) would be easily visible even in heavily obfuscated code. Furthermore, activating at any of those junctures may be sub-optimal for our hypothetical malicious dev's needs. Being able to trigger at point-in-time is incredibly, incredibly powerful (in the negative sense).
Seriously? adding a heavily obfuscated backdoor code would be easy, but adding a heavily obfuscated simple condition code would be difficult?
And the "able to trigger" is as easy as a condition sort of "if certain address sends certain amount".
This is the typical "is it possible?" yes, "is it probable?" almost impossible to happen. And the important question "would DASH be more vulnerable than any other coin?" of course not, in fact it would be less possible with DASH because it has so many critical eyes on top of it that any commit is analyzed in search of something to troll about.