More similar in that they force them to obey the regulations, yes. But regulations cover things like interoperability & anti-competitive behaviour, and here retaliatory actions. I'd very much like _all_ choices to be forced to behave the same w.r.t. not being able to retaliate against protected action, or all be forced to follow the same laws.

There are plenty of ways to differentiate in a competitive market. Good regulations set baselines for fair play, both toward customers and competitors. Whether or not that makes some aspects of those choices more similar isn't really relevant. Or if it is, it's because it makes them similar in good ways. Ways that are pro-customer and pro-competition, but they won't do unless legally required.

I agree that there are plenty of ways competitors could differentiate themselves. But in the current market, I think there are very few competitors, and even fewer ways they currently differentiate themselves. And the most notable recent regulations would eliminate one of the more meaningful differentiations.

Differentiating on percent of app / subscription price taken by app store?

That’s not what I had in mind.

Sure. In the same way that all sports are similar in that most have regulations against fighting.

But we’re not in a situation where there are very few sports, where many people complain about the lack of choice in sports, and where regulators are attempting to eliminate one of the very few meaningful differences between the existing choices.