Scotch oats to substitute Fine Oats in Rum Balls
You should be able to figure out pretty easily if you can eat your Scotch oats raw - just put some in your mouth.  Is it hard as a rock, or soft enough to comfortably chew?

Anyway, Scotch oats, which may or may not be the same thing as Scottish oats (depending on the producer) are typically fairly roughly milled uncooked oat groats. If you got yours from Bulk Barn, it may look like this:



I had not heard of fine oats before - probably because they're typically marketed more as a nutritional supplement than a cooking ingredient.

According to The Protein Works,


  Fine Oats are a low Glycaemic Index (GI) carbohydrate that are considered ideal for providing a slow sustained release of energy for an athletes...fine oats are easily added to protein shakes...many sports nutritionists use them in various recipes such as nutritious homemade bars or cakes.


Two things in that description make me think that Scotch oats won't be a perfect substitute.  First, Scotch oats could probably not be added to a protein shake without being cooked first. Second, I don't believe oats are typically considered to have a low Glycemic Index value.  The Mayo clinic lists them as a "Medium GI" food: Glycemic index diet: What's behind the claims

I don't know if something is done to fine oats to change their nutritional properties, or if this is just a disagreement about Glycemic Index labeling.

If you're not concerned about the Glycemic Index value of your rum balls (and it seems hard to imagine low GI rum balls), this doesn't matter.  The only important thing is whether the texture of the Scotch oats be suitable. My sense is that they will be too firm to chew without cooking. Some rum ball recipes call for brief cooking, which may be enough to soften the Scotch oats. But if yours is a recipe that involves no cooking, and if you have the means, you may want to grind those oats more finely.