It may be a free subscription, but it's still an ongoing, no-opt-out commercial software service relationship with Apple, Inc. That's why it has a Terms of Service [0] – which is effectively a ToS for the iPhone hardware itself, as there is no way to use it without Apple's OS.
(And I think it's noteworthy how that ToS' language bounces freely between "hardware" and "software"; how it fluctuates between "software license agreement" and "by using your iPhone ("device"), you are agreeing to...". Apple hardware and software are fused together: there is no practical difference).
[0] https://www.apple.com/legal/sla/docs/iOS16_iPadOS16.pdf (the iOS ToS)
(And I think it's noteworthy how that ToS' language bounces freely between "hardware" and "software"; how it fluctuates between "software license agreement" and "by using your iPhone ("device"), you are agreeing to...". Apple hardware and software are fused together: there is no practical difference).