Despite being made of gold, not paper, being sold on a site called JM
Bullion and marketing explicitly highlighting its appeal to gold buyers due to gold purity and content, it's not bullion, but paper? I don't follow your reasoning here, and I didn't know bullion required qualifications, I'll have to ask my dealer about that next time.
The face of a Utah Goldback (materially identical to the Breifne gold note in question, produced by
the same company) says, "This Gold Coin Contains 1/x Troy Ounce 24K Gold", so it is self-described as a coin, of all things, suggesting that metal content is, again, the salient point here.
I grant you, it's not exactly a regular bar (ingot seems like a more apt term), but it's 110% not paper. It would appear that there are quite a few gold foil "notes" on the market these days, so maybe a section for that would make sense, though it would probably be dominated by the output of this one company. Part of my reasoning on prioritizing the gold content over the ability to enter dimensions is that I think it's more likely for users to attempt to search for gold items than 65x180mm items; putting the gold content in comments will hamper such searches.
Here are the search results in Fantasy Banknotes for "gold". Some of them do appear to have some gold included, but not a single page specifies gold content and only one specifies fineness. Are these primarily paper with a minor amount of gold, or are they gold foil?