> Hahaha - what a BS argument!

As much as it sounds like a BS argument to you, the argument isn’t actually of Apple’s making. I don’t blame you for thinking otherwise though, it’s mainly poor reporting by Reuters and subsequently 9to5 that fails to explain this.

The EU was first to look at the App Stores separately to determine how many users each store had and if they’d fall under the DMA, primarily driven by the idea that each OS has its own functionality and limitations and different purposes.
I’ll owe you a citation because I don’t have it on hand, but if memory serves me right iOS and its App Store came out as the only one with sufficient EU users.

This was undesirable from the EU’s standpoint as it meant that they weren’t able to regulate the other OSs/App Stored so the EU reversed course and started treating them as one and the same.

Cue Apple, who now appeal this finding, and argue that they are in fact separate. But as said above, that argument isn’t of Apple’s making, that’s how the EU saw it initially as well and how they started their threshold tests.

> And if I have a MacBook, for instance, do I have a choice in downloading the app from the iPad store or the iPhone store? No, there’s just one for my device!

This is not really a relevant argument, as it suggests that storefronts only exist as separate storefronts if you can download from it. The Google Play store is definitely a different store than the Apple App Store, but you can’t download from it.

That said, on Apple Silicon MacBooks you can definitely download apps from the iPhone and iPad App Store.

> And do I have a choice to use a non Apple App Store? No!

On the MacBook? Yes, definitely. You can use Steam for example, or no store, or SetApp, etc, etc.

> So while there might be multiple stores for Apple, there’s only one for my device from Apple

Again, opinion on the argument notwithstanding, this is a non sequitur. Whether you can only use one store on your device says little about it and how Apple’s App Stores are separate. There are actually some decent arguments to be made that Apple’s App Stores are not separate, but I don’t think this is one of them.

> It’s like arguing that any monopoly isn’t actually a monopoly because the company has multiple physical locations. But the consumer has one choice, constrained by geography

This is not a good analogy, because monopoly and monopoly powers are not analogous to running multiple stores. You can run multiple stores, say under two different brands or one for consumers and one for business customers and still be a monopoly for example.

> I’m no lawyer but this is clearly a Hail Mary, perhaps suggested by some law firm to get a little more money out of Apple

I used to be one in a former life, specialized in EU law and other international law, and for better or for worse this is not a Hail Mary. It’s actually a pretty solid argument within the context of the DMA because of the way DMA determines gatekeeper status (which was why the EU originally looked at the OSs and storefronts separately).

That said, I think there are some bigger issues with the DMA and how it’s applied, suggesting that the EU is bending some of the regulations to target specific companies and services beyond plausible deniability.
We’ll have to see how those shake out in court, because that’s generally a no-no.

I expect some degree of compliance and some degree of long legal proceedings to get some clear boundaries set for both companies like Apple as well as the EU. The latter will then try to amend the legislation in an attempt to achieve their goal and the cycle will start over. With some luck by 2030 the dust has settled and everyone knows what they’re up against.