I'm not sure why you feel qualified to comment on the legal aspects on this case based on just a primitive understanding of offer and acceptance (which isn't the point of contention here). You can't have an enforceable contractual term that is illegal, even if both parties have agreed to it. The legal issue is whether Apple's ToS contravenes some aspect of competition law.
IANAL but my understanding of antitrust cases is that voluntary consent to a EULA is indeed a relevant factor in determining market power for antitrust claims. See the discussion in Blizzard Entertainment Inc. v. Ceiling Fan Software LLC:
> Blizzard raises this argument in its motion, contending that Defendants cannot establish antitrust claims based on its users' voluntary consent to the EULA and TOU. (Mot. Br. 22–23.) Although Blizzard does not argue this point in the market power analysis, the Court finds that this discussion is applicable to whether the market power requirement is established. Blizzard cites Newcal, Queen City Pizza, Inc. v. Domino's Pizza, Inc., 124 F.3d 430, 441 (3d Cir.1997), and Apple Inc. v. Psystar Corp., 586 F.Supp.2d 1190, 1201 (N.D.Cal.2008), to show that Defendants cannot base its claims on the aftermarket restrictions. ( See Opp'n Br. 17.) These cases explain that the law prohibits an antitrust claimant from asserting an antitrust claim “resting on market power that arises solely from contractual rights that customers knowingly and voluntarily gave to the defendant” when they purchased the initial tying product.
