Whether the app store is "inextricably tied" to Apple's platforms is beside my point. The state could simply force Apple to allow other app stores, or to write into law a maximum profit margin (similar to profit caps on the health insurance industry in Obamacare), or require worker representatives on the board of directors, or so many other things to keep one of the largest firms in the world in check.

Your point was that smartphones would have existed without Apple making the iPhone but it doesn't make any sense as a response to what I said. I'm not making an argument about market definitions that would concern an antitrust regulator or court, but the nature of the relationship between the platform and sellers being materially different with Apple than GrubHub. And thus who does more work to actually earn their take rate.