Some of that is on Rivera, but not all of it. hence, his 1-12 record may be closer to 1-4 for games in which he is directly responsible. Not good, but not catastrophic. And again, what indications do we have that Harbaugh is any better of a close game coach?
I think it's higher than 1-4 (even if that's outside the variables, cause Rivera increases them against himself).
However, to answer your question: Here's what makes Rivera a bad, worse coach than Harbaugh, adding to that close loss total of his.
Though Rivera knows he's not the best game manager, especially in tight games. He consistently plays not to lose, when he has big leads, ultimately leading to the opposition coming back, and Rivera losing those games. Now if you know, you're not the best game manager, than why not keep your foot on the accelerator pedal, so you don't have to face/worry about making those decisions in the first place? That makes sense, right? But Rivera doesn't.
My second point is: If Rivera knows/knew he needed an experienced HC to help guide him. Then how come he didn't hire one to help him this year?
The true definition of insanity, is to do the same thing over and over again, and expect different results. And that adds to his close loss futility. Of course he may change, learn. However, you know what I'm saying as well.
Somehow, I don't expect Harbaugh to be as dumb, with simple decisions. He couldn't be, and be where he is right now. Just face it!