I'm aware of that article, but it's a bit old by now, and things have moved on. We now have Metalman, for example.
If Irish Pale Ale is distinct from other styles, I'd say it is a style all of its own, but it needs to be recognised by some official body (BJCP?).
My own assessment (i.e. my 2c!) is that it is a spin off of American Pale Ale, but with the main difference being the ABV. APA is 4.5%-6.2%, whereas I'd put IPA at 4.2%-4.7%. APA is typically slightly darker, minimum 5 SRM (which is light) whereas IPA could maybe get as low as 3. Hops profile in an IPA tends to be biased towards American, but UK or European hops do usually get a look in, which is not really a trait of APA.
In summary, IPA is lower abv, and lighter in colour than an APA, possibly with a "mid-Atlantic" hop profile (I made that up), otherwise similar, but sufficiently different to be its own style.
APA style guideline:
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www.bjcp.org/2008styles/style10.php