I had the same cofusion as you, zinger, when I first attempted ganache.
Sorry, Kelly, but an ounce is not an ounce. There are weight ounces and there are volume, or liquid, ounces. For example, a one cup measure holds 8 ounces by volume. If you fill it with cream you get eight liquid/volume ounces of cream. But if you weigh that cream on a scale it will weigh about 8 1/2 oz. Different liquids will weigh different amounts depending on their density.
If you fill that same 8 ounce cup with feathers or sand, each will have different weights as there is no correlation between the two different kind of ounces...weight and volume.
One 8 oz cup of chocolate actually weighs 10 oz if it's melted, less if it's chopped. So it does depend on whether it's chips or chunks or melted or blocks because each takes up a different amount of space in an 8 oz cup.
So you are correct, these recipes are all comparing apples and oranges.
The best I can figure out from recipes that give both the ratio and the specific amount is that they are measuring the cream by volume compared to the chocolate by weight. Of course, when you do it this way, the ratio is of apples to oranges.
If you did use weight measures for both as Kelly references (1 oz cream to 3oz chocolate) it doesn't match up with the references I can find that mention actual amounts used. I've even seen recipes that call for 20ml cream to 60 mg chocolate...clearly a weight to volume 3 to 1.