Would it not show up on the misfire monitor if it was a ignition coil?
Actually, no.
The 2007Toyota Matrix I'm dealing with(almost the same thing as a Pontiac Vibe) did not have any codes I can say it directly caused by the coils themselves.
It did throw a P0171 when I was revving the engine hard, but that could have been the injectors, which simultaneously wore with the coils. Had I not driven "angry", no code would have even been thrown, although fuel trims did show a lean condition even after the P0171 cleared itself.
The injectors and/or coils might have been already worn 100k and 10 years before this check engine light. Every time I disconnected the battery, the car's default computer mix for fuel and air would cause it to stall itself out for the first couple of starts. Given the age of your is similar to the one I'm dealing with, would it be fair to presume that has happened to your vehicle?
I replaced the injectors first, and I did notice some slight improvement, but nowhere near the "insta-crank" of a new vehicle. I did not touch the coils at first.
I also had only one Denso 673-1300 coil. I removed one of the old coils and installed this one(the same one I took readings on). Cranking improved noticeably to only three turns or less, and that's just one new coil. If I replace the other coils, I think I can get back to an "insta-start" as if the car was back on the dealership lot.